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THE 

LONDON AND EDINBURGH 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



CONDUCTED BY 



SIR DAVID BREWSTER, K.H.LL.D.F.R.S.L.&E.&c. 
RICHARD TAYLOR, F.L.S.G.S. Astr.S.Nat.H.Mosc.&c 

AND 

RICHARD PHILLIPS, F.R.S.L.&E.F.G.S. &c. 



" Nee aranearum sane textus ideo melior quia ex se fila gignunt, nee nostet 
vilior quia ex iillenis libamus ut apes." Just. Lips. Monit. Folk. lib. i. eap. I. 



VOL. XIIL 



NEW AND UNITED SERIES OF THE PHILOSOPHICAL MAGAZINE, 
ANNALS OF PHILOSOPHY, AND JOURNAL OF SCIENCE. 

JULY— DECEMBER, 1838. 



LONDON: 

painted by r. and j. e. taylor, red lion court, fleet street: 

sold by longman, orme, brown, green, and longmans; cadell; 

baldwin and cradock; sherwood, gilbert, and piper; simpkin 

and marshall; whittaker and co.j and s. highley, 

London: — by adam and charles black, and 

thomas clark, edinburgh; smith and son, 

glasgow; hodges and smith, dublin : 

AND G. W. M. REYNOLDS, PARIS. 




The Conductors of the London and Edinburgh Philosophical Magazine 
have to acknowledge the editorial assistance rendered them by their friend 
Mr. Edward W. Bravley, F.L.S., F.G.S., Corr. Mem. Roy. Geol. Soc. of 
Cornwall, Hon. Mem. S. Afric. Inst.; Librarian to the London Institution. 



CONTENTS OF VOL. XIII. 



NUMBER LXXIX.— JULY, 1838. 

Page 

Education of Students in Civil Engineering and Mining in the 

University of Durham 1 

Mr, R, Potter on the Radii and Distance of the Primary and 
Secondary Rainbows, as found by Observation, and on 
a Comparison of their Values with those given by Theory. . 9 
Lieut. -Col. Emmett's Meteorological Observations taken at St. 
George's, Bermuda, in the December half-year of 1837 ; in- 
troduced by Corrections of Observations for the June half- 
year 12 

Dr. Golding Bird's Experimental Researches on the Nature and 

Properties of Albumen, &c 15 

Prof. J. F. W. Johnston on the Composition of certain Mineral 

Substances of Organic Origin. No. V, Elastic Bitumen .... 22 
Prof. J.F.W. Johnston on the Separation of the Oxalic from 

other Organic Acids 25 

Prof. R. Hare on the Reaction of the Essential Oils with Sul- 
phurous Acid, as evolved in union with .^Ether in the Pro- 
cess of -^therification, or otherwise 28 

Mr, C. HoltzapfFel on a Scale of Geometrical Equivalents for 

Engineering and other Purposes 32 

Mr, R. Laming on the primary Forces of Electricity 44 

Mr. C. Binks on some of the Phsenomena and Laws of Action 
of Voltaic Electricity, and on the construction of Voltaic 

Batteries, &c 54 

The Herschel Dinner 75 

Action of Light on Solution of Cyanogen 77 

Bichromate of Perchloride of Chromium 78 

Meteorological Observations for May 1838 79 

Meteorological Observations made at the Apartments of the 
Royal Society by the Assistant Secretary Mr. Roberton ; 
by Mr. Thompson at the Gardens of the Horticultural Society 
at Chiswick, near London ; by Mr. Veall at Boston ; and by 
Mr. Dunbar at Applegarth Manse, Dumfries -shire 79 



NUMBER LXXX.-AUGUST. 

Mr. Ivory on the Conditions of Equilibrium of a Homogeneous 

Planet in a Fluid State 81 

Mr. Lubbock on a Property of the Conic Sections 83 

Mr. D. Waldie's Experimental Researches on Combustion and 

Flame ^6 

Prof. J. D. Forbes's Researches on Heat. Third Series 97 

Dr. J. Apjohn on a new Compound, consisting of Iodide of 

Potassium, Iodine, and the Essential Oil of Cinnamon 113 

Mr. T. Richardson's Researches upon the Composition of Coal 121 

a2 



iv CONTENTS. 

Page 
Mr. J. J. Griffin's Arithmetical Analysis of mixed Salts of Po- 
tassium and Sodium 132 

Mr. C. Binks on some of the Phsenomena and Laws of Action 
of Voltaic Electricity, and on the construction of Voltaic 

Batteries, &c. (continued) 135 

Proceedings of the Royal Society 146 

Cause of the Circulation of the Chara 153 

Action of Plants on the Azote of the Atmosphere 154 

Proportions of Animal and Earthy Matter in Human Bones . . 155 
On the Ammoniacal and other Basic Compounds of the Copper 

and Silver Families, by Professor Kane 156 

Meteorological Observations 159 



NUMBER LXXXL— SEPTEMBER. 

Prof. Schcenbein's Discussion of M. Fechner's Views of the 
Theory of Galvanism, with reference, particularly, to a Cir- 
cuit including Two Electrolytes, and to the relations of In- 
active Iron 161 

Mr. C. Binks on some of the Phsenomena and Laws of Action 
of Voltaic Electricity, and on the Construction of Voltaic 

Batteries, &c. (continued) 171 

Prof. J. D. Forbes's Researches on Heat. Third Series 180 

Mr. G. Gulliver's Researches on Suppuration 193 

Mr. J. J. Griffin's Instructions for the Qualitative Analysis of 

Soluble Salts 202 

G.T. H. Fechner's Justification of the Contact Theory of Gal- 
vanism 205 

Mr. J. T. Graves on a new and general Solution of Cubic Equa- 
tions 217 

Prof.T. Graham's Note on the Constitution of Salts 219 

New Books ; — A brief Account of the Life, Writings, and In- 
ventions of Sir Samuel Morland, Master of Mechanics to 
Charles the Second; — Rara Mathematica; or, a Collection 
of Treatises on the Mathematics and subjects connected with 

them, from ancient inedited manuscripts. No. 1 221 

Proceedings of the Royal Society, British Association for the 

Advancement of Science, and Geological Society. . . . 222 — 225 
The Swiss Association for the Advancement of Natural Science 233 
Errors in the Nomenclature of certain Stars in Groombridge's 

Catalogue 233 

On the Chemical Reactions of Water by M. Kuhlman 234 

On Sugars, by M. Peligot 237 

Succisterin 238 

Meteorological Observations 239 

NUMBER LXXXIL— OCTOBER. 
Prof. J. W. Draper's Remarks on the Constitution of the At- 
mosphere 241 



CONTENTS. V 

Page 
M. Quetelet's Observations on Shooting Stars on the Nights 

of the 9th, 10th, and 11th of August 1838 252 

Dr. Schoenbein's Conjectures on the Cause of the peculiar Con- 
dition of Iron 256 

Dr. J. Apjohn on the Specific Heats of the Gases as deduced 
by himself compared with the more recent Results of Dr. 

Suerman 261 

Mr. Ivory's Remark on an Article of M. Poisson's Trait4 de 

M^canique (No. 593. Edition 2nde) 274 

Mr. C. Binks on some of the Phsenoraena and Laws of Action 
of Voltaic Electricity, and on the Construction of Voltaic 

Batteries, &c. {continued') 276 

Mr. Faraday's Experimental Researches in Electricity. — 

Eleventh Series 281 

Proceedings of the Geological Society 299 

Continuation of the Scientific Memoirs 310 

Synaptasin 310 

Composition of the Blood 311 

On the Iodide of Amidin, by M. J. L. Lassaigne 312 

New Compound of Sulphate of Magnesia and "Water 313 

On Chloretheral, by M. Felix D'Arcet 313 

Formio-Benzoilic Acid 315 

Proportions of Gluten in Grain 315 

Oxide of Phosphorus 315 

Borates of Potash, by M. Laurent 317 

Cyanide of Gold 318 

Meteorological Observations 319 



NUMBER LXXXIII.— NOVEMBER. 

Mr. Ivory on a Principle laid down by Clairaut for deter- 
mining the Figure of Equilibrium of a Fluid, the Particles of 
which are urged by accelerating forces 321 

Prof. J. F. W. Johnston on a new Compound of Sulphate of 
Lime with Water 325 

Prof. J. F. W. Johnston on the Composition of certain Mineral 
Substances of Organic Origin. No. VI. Guyaquillite 329 

Mr. Laming on the primary Forces of Electricity 333 

Dr. J. Apjohn on the Specific Heats of the Gases as deduced 
by himself compared with the more recent Results of Dr. 
Suerman 339 

Mr. C. T. Jackson's Chemical Analysis of Meteoric Iron, from 
Claiborne, Clarke County, Alabama 350 

Mr. Faraday's Experimental Researches in Electricity. — • 
Eleventh Series {continued) 355 

G. T. H. Fechner's Justification of the Contact Theory of 
Galvanism 367 



VI CONTENTS. 

Dr. Golding Bird's Observations on some peculiar Properties 
acquired by Plates of Platina, which have been used as the 

Electrodes of a Voltaic Battery 379 

Proceedings of the Geological Society, and Royal Geological 

Society of Cornvi^all 386 

Reagent for the Detection of Sulphurous Acid in the Hydro- 
chloric Acid of Commerce, by Girardin 392 

Processes for preparing Lithia, by Fuchs , 393 

New Double Salt of Zinc and Potassium, by Anthon 393 

Reagent for Nitric Acid and Nitrogen, by Desbassayns de 

Richemont '. 393 

Formate of Soda, as a reducing Substance for metallic Poisons 

(Arsenic) 394 

On the Transparency of Carbon, by Degen 394 

Preparation of arseniuretted Hydrogen, by Vogel 395 

Tungstate of Tungsten and Potash 395 

Analysis of Serum of Blood drawn from a diabetic Patient, by 

Dr. G. O. Rees 395 

Analysis of the Liquor Amnii 395 

Stearopten of Turpentine 396 

Metallic Pectates 397 

Portrait of Prof. Faraday 399 

Portrait of Robert Brown, F.R.S., &c 399 

Meteorological Observations 399 



NUMBER LXXXIV.— DECEMBER. 

Prof. Dr. Jacobi on the Galvanic Spark 401 

Prof. J. F. W. Johnston on some apparent Exceptions to the 
Law, that like CrystalUne Forms indicate like Chemical 
Formulae 405 

Mr. Faraday's Experimental Researches in Electricity. — 
Eleventh Series 412 

Mr. W. R. Grove on a new Voltaic Combination 430 

Mr. J. B. Nevins on the Reduction of the Chlorides of Mercury 
when mixed with Organic Substances 431 

Rev. E. Craig on the Process for obtaining the Bichromate of 
the Perchloride of Chrome, as viewed under the Microscope 433 

Mr. D. F. Gregory on the Experiments detailed in Mr.Waldie's 
Paper on Combustion and Flame, inserted in the Lond. and 
Edinb. Phil. Mag. for August 1838 434 

On a certain Difficulty connected with the Demonstration of 
Euclid, Book L Prop. 29 434 

Mr. J. P. Gassiot on a remarkable Difference in the Heat at- 
tained by the Electrodes of a powerful Constant Battery : in 
a Letter to Mr. Brayley 436 

Dr. R. Kane on the Composition of Essential Oils 437 

Prof. J. J. Sylvester on the Motion and Rest of Fluids 449 



CONTENTS. VII 

Page 
Prof. J. J. Sylvester on an Extension of Sir John Wilson's 

Theorem to all Numbers whatever 454 

Proceedings of the Royal Society 454 

Xyloidine 467 

Determination of Iodine in Kelp 468 

Polarization of Platina Electrodes 469 

Sulphocyanide of Potassium as a test for Strychnia 470 

Analyses of Pectic Acid, by M. V. Regnault 47 1 

Pectates of Potash, Soda, and Ammonia 472 

On the Decomposition of Siliceous Minerals by means of Hy- 
drofluoric Acid 473 

On the Separation of Compounds of the Oxides of Antimony 

and Lead 473 

Letter from Professor Johnston on the Analysis of the Resins 474 

Analysis of Comptonite 475 

Action of Chlorine on Acetic Acid 475 

Action of Chloride of Zinc on Alcohol 475 

Combination of Azote with Metals 476 

Solubility of Binoxide of Mercury in Water 477 

Decomposition of Lithic Acid by Nitric Acid 477 

Lactate of Urea 478 

Caoutchouc in Plants , . 478 

New Anomalous ReptUe 479 

Meteorological Observations 479 



NUMBER LXXXV.— SUPPLEMENT. 

Index 481 

Genekal Index to the London and Edinburgh Philoso- 
phical Magazine and Journal of Science, vol. i. to xii. 



PLATES. 

I. Illustrative of Mr. Waldie's Researches on Flame, 

II. and IV. Illustrative of Professor Forbes's Researches on Heat, Third 

Series. 
III. Illustrative of Mr. Richa&dson's Researches upon the Composition 
of Coal. 



ERRATA. 



Page 45, Art, 34. line 8, /or directly rend inversely. 
Page 395, line 11, /or precombined read uncombined; 



THE 

LONDON AND EDINBURGH 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



JULY 1838. 



J. Education of Students in Civil Engineering and Mining it. 
the University of Durham.* 

IT has. long been a subject of regret that no institution 
existed in England in which young men might receive an 
education which should peculiarly fit them for the higher 
branches of the profession of a Civil Engineer. That pro- 
fession is comparatively of recent origin. It has been formed 
by the exigencies of the times, and has had to struggle with 
great disadvantages. The names of Smeaton, Brindley, and 
others recall to our minds the difficulties which those men 
of masterly abilities had to encounter, in order to devise the 
means and create the instruments necessary to accomplish 
the purposes which their genius conceived. A portion of this 
difficulty still subsists; while the attainments necessary to 
enable the engineer to meet the emergencies which he has to 
encounter, have continually become more varied and exten- 
sive. 

The construction of canals, harbours and railroads, the 
successful application of steam to the purposes of navigation 
and of locomotive engines on land, the increased activity in 
opening out the treasures of coal and other minerals, in si- 
tuations hitherto deemed inaccessible, have combined to offer 
a field of almost boundless extent for the exercise of talent of 
the highest order. In the meanwhile the profession of civil 
engineer has risen in the scale of national importance, in 
consequence of the immense capital employed under his di- 
rection. In no other profession, with the exception of that 
of the law, are so many questions of pecuniary importance 

* Communicated by the Rev. Prof. Chevallier and Prof. Johnston. 
Phil Mag. S. 3. Vol. 13. No. 79. July 1838. B 



2 Education in Civil Engineeriiig and Mining 

submitted to the judgement of one man. In all public works 
unlimited confidence must be reposed in the skill and inte- 
grity of the civil engineer. If a company is formed, the in- 
dividuals who compose it, and even the greater part of the 
directors, cannot be competent to form an opinion upon many 
of the questions which are of vital importance to the success 
of their undertaking. The peculiar obstacles to be encoun- 
tered, the readiest and most efficacious means of overcoming 
them, or the most dexterous way to elude them, all require 
the union of long practice with natural talents and a cultivated 
mind. An error of judgement may entail a loss of millions of 
capital ; .and if such misconduct could be conceived possible, 
the want of integrity in the engineer would be ruinous to his 
employers. 

The profession of civil engineer is also requiring from day 
to day a more extended range of information. Every part of 
mechanical science, as exercised in the construction of ma- 
chinery, has received, and is still constantly receiving, great 
improvement. Questions arise respecting points which have 
only of late become a part of the civil engineer's practice. 
The relative position of the surface of very extended tracts of 
country, and the easiest lines of communication from place to 
place, require an extent of survey, which hitherto has been 
confined to the great geodetical operations undertaken for 
purposes purely scientific, accompanied with a minuteness of 
individual detail which even those purposes do not require. 
The extended processes of mining call for a knowledge of 
geology, mineralogy, chemistry, and metallurgy ; and the 
constantly increasing boldness of speculation in undertakings 
of great extent, gives rise to practical problems of the greatest 
difficulty, and leads to the construction of works which will 
vie with the most magnificent structures of antiquity. 

Yet, with all these increasing demands upon the skill and 
attainments of the civil engineers of this country, there has 
hitherto been found a great deficiency in the means of ac- 
quiring the requisite information. The education of young 
men at school has usually been too elementary to be of much 
service. The course of study pursued at the Universities has 
been too general and theoretical to be adapted to the parti- 
cular wants of the young civil engineer ; and although many 
valuable courses of lectures have been constantly given in the 
Universities on subjects intimately connected with the theory 
and practice of engineering and mining, those who are best 
acquainted with academical studies have been of opinion that 
the knowledge requisite for practical men would be more 
advantageously cultivated elsewhere. Hence those civil en- 



in tJie University of jyurham. 3 

gineers who have risen even to the highest rank in their pro- 
fession have encountered the greatest difficulties in the early 
part of their career, for want of sufficient training in the 
course of their education. And although men of real talent 
and great perseverance have by the effiarts of self-taught 
genius successfully mastered the obstacles thus unnecessarily 
thrown in their way, there can be little doubt that some even of 
these men would have received benefit from more systematic 
training, and that many others, who, under a proper course 
of instruction in their youth, would have attained eminence 
in their profession, have never risen above mediocrity. 

The University of Durham is the first public body which 
has attempted to supply this deficiency in the system of edu- 
cation pursued in this country. It appeared to them that it 
was practicable to engraft the peculiar studies connected with 
civil engineering and mining upon the more general course 
of academical reading; and that, if such a union could be 
made, great benefit might be anticipated from the association 
of young men intended for the higher departments of civil 
engineering, with those who were destined for the learned 
professions, or for other stations in the higher or middle 
ranks of life. With this view, it was deemed desirable that 
the class of civil engineers should not form a separate body 
in the University, composing a college appropriated to them- 
selves, but be admitted on the same footing as other students, 
subject to the same discipline, and engaged in a course of 
study which should be assimilated, as far as was practicable^ 
to the general system of the University. i 

The following Regulations were accordingly prepared after 
much deliberation, and passed by the Senate and Convoca- 
tion, in November 1837. 

Regulations for Students in Civil Engineering, in the Univer* 
sity of Durham^ passed by the Senate and Convocation, 
Nov. 22, 1837. 

1. Students shall be admissible, in conformity with the Re- 
gulations, Title ii., § 1, 2, 3, as Members of the University, 
subject to the ordinary University and College disciplincj to 
go through a course of instruction in Civil Engineering. 

2. No such Student shall be admitted, unless he has passed 
an Examination in the Latin language, in Arithmetic, and in 
the Elements of Mathematics. 

This examination shall be conducted by two Examiners 
appointed by the Warden. 

3. Every such Student shall be placed, like other Students, 
under a Tutor named by the Warden, The Tutor shall 

B2 



4j Education in Civil Engineering and Mi7iing 

direct his private studies, and shall have charge of his con- 
duct and religious instruction. 

4. The course of study for Engineer Students and the se- 
veral lectures designed for them shall be under the imme- 
diate superintendence of the Professor of Mathematics, subject 
to the control of the Warden and Senate. 

5. The full course of study shall extend over three years ; 
and shall embrace the several subjects which relate to the 
theory and practice of Civil Engineering and Mining. 

6. Engineer Students, who have completed their course, 
shall be admissible, by Grace of the University, to the Aca- 
demical rank of Civil Engineer. 

Engineer Students may, at an earlier period, receive Certi- 
ficates of competency in the subjects in which they have been 
examined, as hereafter specified. 

7. No Grace for admission to the rank of Civil Engineer 
shall be granted, unless the petitioner has passed three Public 
Examinations. The first of these shall be for Students who 
are in their third term of residence, at least ; the second for 
such as have passed the first, and are in their sixth term of 
residence, at least ; the third for such as have passed both the 
former, and are in their ninth term of residence, at least. 

Yet any Engineer Student, who, at his admission to the 
University, shall pass the first Public Examination thus ap- 
pointed for Engineer Students, shall be placed in the same 
position with regard to all terms and examinations relating 
to Engineer Students only, as if he had already kept three 
terms. 

8. The first two of these Examinations shall be conducted 
by two or more Examiners nominated annually by the War- 
den, and approved by Convocation ; and shall be directed to 
the subjects fixed by the Senate eleven months, at least, be- 
fore. 

After the second of these Examinations, any one who is 
specially recommended by the Examiners may obtain a formal 
Certificate from the Warden ; this Certificate being limited 
to the particular subjects in which he has proved his com- 
petency. 

9. The third and final Examination shall be conducted by 
three Examiners, at least, nominated by the Warden, and 
approved by Convocation ; and shall be directed to the sub- 
jects fixed by the Senate eleven months, at least, before : pro- 
vided always that every such Student shall then pass an exa- 
mination in a modern language, or in some one Latin or 
Greek work, melioris avi et notes i the language or work to 
be selected by himself, but approved by the Senate. 



in the University of Durham. S 

10. All those who satisfy the Examiners, at each of these 
Examinations, shall be classed. The Senate shall have power 
to determine hereafter the subjects in which proficiency shall 
be deemed indispensable, and the nature of the classifica- 
tion, 

11. Any student in arts, upon passing his first examination 
for the Degree of B.A., may proceed as an Engineer Student 
of the second year; and upon passing his second examination 
for the Degree of B. A., may proceed as an Engineer Student 
of the third year. 

12. Any Engineer Student, who is recommended by his 
College, may petition the University, that terms which he has 
kept by residence as an Engineer Student may count towards 
the Degree of B. A. ; and that the Examination passed by him 
in his third term of residence, at least, may be received instead 
of the first Examination for the Degree of B.A. ; and the 
Examination passed by him in his sixth term of residence, at 
least, instead of the second Examination for the Degree of 
B.A. 

13. The Warden and Senate shall have power to declare, 
in the course of Easter Term, 1838, that any Engineer Stu- 
dent, who shall have kept Epiphany Term, 1838, shall be 
regarded, with reference to all terms and examinations rela- 
ting to Engineer Students only, as if he had kept also Mi- 
chaelmas Term, 1837. 

Orders made hy the Senate, for carrying the above Regulations 
into effect. 

1. The Course of Study for Engineer Students shall em- 
brace the following subjects : — 

Arithmetic. Practical Mapping, and Ar- 
Algebra. chitectural Drawing. 

Euclid. Theoryof Perspective and Pro- 
Logarithms, jections. 

Plane Trigonometry. Hydrostatical and Hydraulical 
Solid Geometry. Instruments in general. 

Analytical Geometry. The Steam Engine. 

Theoretical and Practical Optical Instruments. 

Mechanics. Theoretical and Practical Che- 
Differential and Integral mistry. 

Calculus. Theory of Heat. 

Dynamics. Mineralogy. 

Hydrostatics and Hydraulics. Metallurgy. 

Pneumatics. Geology. 

Surveying, Levelling, use of The French, German, Spanish, 

Instruments. and Italian Languages. 

2. All Enghieer Students who do not learn one of the 



6 Education in Civil Engineering and Mining 

above-named Modern Languages shall attend Lectures in 
Latin or Greek during one term, at least, in each of their first 
two years of residence. 

3. Besides keeping the ordinary Academical Terms, Engi- 
neer Students shall reside during the Easter vacation ; and 
the Lectures shall be so arranged as to provide employment 
for them during their residence. 

4<. Engineer Students shall, during the first six terms of 
their residence as such, pay for tuition the sum of 10^. 10s. in 
each term ; and during their further residence as such, the 
sum of 7^. in each term. 

5. Every Student admitted to the Academical rank of Civil 
Engineer, shall receive a Certificate of such admission under 
the Common Seal of the University. The Certificate of 
competency given to Students after their second examination, 
(granted by the Warden, in conformity with section 8 of the 
Regulations of Nov. 22nd, 1837,) shall contain the names of 
the examiners on whose recommendation it is given. 

6. The first two of the Public Examinations shall take place 
in the month of October, and the third and final Examina- 
tion during the Easter Term, in each year. 

7. Engineer Students shall pay a fee of \l. on admission 
to each of the first two Public Examinations ; a fee of 21. on 
admission to the third and final Examination ; and a fee of Si. 
on admission to the rank of Civil Engineer, or on receiving a 
Certificate of competency. 

8. Any Student in Arts may be admitted to attend any 
Course of Lectures designed for Engineer Students, upon the 
payment of such fee as the Senate shall -hereafter direct. 

9. Any Engineer Student may be admitted to attend any 
Course of Lectures designed for Students in Arts, upon such 
terms as the Senate shall hereafter direct. 

The Regulations referred to in section 1, are as follows : — 
Of Admission. 

1. No one shall be held to be a Member of the University 
who has not been matriculated, that is, whose name has not 
been placed on the Register of the University by the authority 
of the Warden. 

2. No Student shall be matriculated, unless he is a Mem- 
ber of the existing College, or of some other recognised Col- 
lege, Hall, or House, nor unless he has produced to the 
Warden satisfactory testimonials of character. 

3. Every Student, at the time of his matriculation, shall 
subscribe a declaration of obedience to the Authorities of the 
University. 

As this is the first plan of the kind which has been attempted 



in the University of Durham. 7 

in this country, and many of the details may be interesting 
to some who are not familiar with academical studies, it may 
be desirable to state somewhat more at length the nature of 
the studies pursued. 

The students at the time of their admission are required to 
be well acquainted with arithmetic, both as applied to com- 
mercial purposes and as used in the ordinary computations of 
engineering. They pass an examination also in the Latin 
language and in the elements of mathematics. If, on admis- 
sion, a student is sufficiently advanced to pass the examination 
appointed for those engineer students who have already resided 
for a year, he is entitled to proceed at once in the course of 
reading intended for those who are then commencing their 
second year's residence, and to receive his final certificate at 
the end of two years' residence instead of three. 

The lectures for the different years are arranged according 
to the degree of proficiency which the students have attained, 
beginning with geometry and the elementary parts of mathe- 
matics ; arithmetic^ especially as relating to the course of ex- 
change, vulgar and decimal fractions and the extraction of 
roots ; and proceeding in the course of subjects pointed out 
in the regulations. The modern languages which are gene- 
rally taught are French and German. During their whole 
course the students are engaged in practical surveying, level- 
ing, and planning ; and in acquiring the familiar use of instru- 
ments, under the superintendence of an experienced civil engi- 
neer; and they receive instruction in crystallography, mi- 
neralogy, geology, and metallurgy. The local position of the 
city of Durham, in the immediate neighbourhood of the 
largest coal-mines in the world, at no great distance from the 
lead-mines of the western part of the county, and in a district 
intersected in all directions by railroads carried through very 
difficult lines of country, gives peculiar advantages for ac- 
quiring a practical insight into all the details of the ordinary 
operations of civil engineering and mining ; and full use is 
made of these facilities. 

The proficiency of the students is tested by public exami- 
nations every year. At the close of their three years' course, 
honours are given to those who distinguish themselves ; and 
those who have passed all the examinations are admitted to 
the academical rank of civil engineer, and receive certificates 
to that effect. Certificates of competency in any particular 
branch of study may be received at an earlier period. 

It is hoped that the course of instruction thus pursued will 
secure for the student a sound knowledge of those parts of 
theoretical mathematics and of the sciences of observation, 
which are essential for the scientific engineer, and at the same 



8 Education in Civil Engineering and Mining. 

time give him a perfect acquaintance with all the necessary 
practical details. 

It has already been observed that the engineer students are 
subject to the same discipline and moral control as the other 
students in the University, an advantage which will be duly 
appreciated by those parents and others who are desirous of 
securing for a young man the advantage of a sound education, 
under wholesome control, and in the society of young men of 
the same age intended for other professions. 

By the regulations provision is made for any engineer stu- 
dent to proceed to the degree of bachelor of arts, on passing 
the requisite examinations for that purpose. There are seve- 
ral scholarships in the University, to which engineer students, 
as well as others, are eligible. 

The class of engineers was opened in January 1838, and at 
present consists of eight students. The academical year, 
consisting of three terms, begins in October ; and the lectures 
are arranged so that the course of instruction commences at 
that time. 

The fees payable by engineer students for tuition are 1 0/. 1 Os. 
in each term. This includes all payments to the professors 
and other officers of the University, and gives the student 
admission to all the lectures given to his class. The students 
have rooms in the University College, and dine in the college 
hall. It is understood that the whole expense of residence 
during the academical year, including tuition, certainly need 
not exceed lOOZ. 

It will be borne in mind that the new course of study esta- 
blished by the University of Durham is such as to form not 
merely a school of civil engineers in the ordinary sense of the 
term, but'also a School of Mines, in which persons likely to be 
through life engaged either in excavating the mineral wealth 
of various kinds with which the country abounds, or in con- 
verting the raw mineral into an article of commerce, may re- 
ceive the elements of the several branches of knowledge which 
their pursuits may require. For the especial benefit of the 
latter class of persons it is provided that at a certain period 
in the course of study a more undivided attention shall be 
given to the theory and processes of metallurgy in its various 
branches than is considered at all necessary for the engineer 
students as a body. The importance of this regulation will be 
understood by those who are aware of the many desiderata and 
unexplained circumstances which the smelter of iron, lead, tin, 
or copper can detail, or of the national waste of material with 
which even tlie most improved processes are attended*. 

* Our readers will remember that the importance of establishing a School 
of Mines in this country has long been urged by Mr. John Taylor, Treas. 



Mr. Potter on the Primary and Secondary Rainbotios. 9 

II. On the Radii and Distance of the Primary and Secondary 
Rainhoisos, as found by Observation, and on a Comparison of 
their Values with those given by Tlteory. By R. Potter, 
Esq., M.A* 

THHE explanation of the rainbow which Sir Isaac Newton 

has given in the second part of *the first book of 

Opticks,' appeared one of the happiest appHcations of his 

freat optical discovery, the unequal refrangibility of light. It 
as, however, been long observed that there are frequently 
supernumerary bows attending the principal ones, and of 
these the theory of Sir Isaac Newton gives no solution. It 
was reserved for Dr. Young to show that they were results of 
the principle of interferences. (See his Lectures on Natural 
Philosophy, or Phil. Trans, for 1803.) But notwithstanding 
the satisfactory manner in which all the phaenomena of the 
rainbow appeared to be accounted for, when the interference 
of the light was taken into consideration, yet the problem 
continued to be discussed in our optical treatises according 
to the old method, and Dr. Young's theory, like most of his 
other fine discoveries, did not receive the notice it deserved. 

In the year 1835, I re-discovered that the solution of these 
phaenomena involved the principle of interferences, without 
knowing what Dr. Young had written, and presented a paper 
to the Cambridge Philosophical Society, which is printed in 
the sixth volume of the Transactions, in which I undertook 
to show that the problem belonged to physical optics. Near 
the close of that paper will be found an intimation that the 
ordinary rainbows might not eventually be found in the posi- 
tions which had hitherto been assigned to them, by Dr. 
Young as well as by all others. 

My views with respect to interference on the corpuscular 
theory of light (see Lond. and Edinb. Phil. Mag. vol. ii. p. 81. 
and ' Correspondance Mathematique et Physique de I'Obser- 
vatoire de Bruxelles,' 2^ livraison, tome 8.) had led me to ex- 
pect this, and I had, at the time of writing that paper, exa- 
mined Sir Isaac Newton's discussion sufficiently to convince 
myself, that there were abundant grounds for anticipating a 
full confirmation when I had time to pursue the investigation 
more completely. 

In the beginning of the year 1836, I compared the mea- 

Geol. Soc. whose Prospectus on the subject will be found in Phil. Mag., 
First Series, vol. Ixvi. p. 137, and in his " Records of Mining." Mr. H. 
English has also repeatedly brought the same subject before the public in 
his Mining Review. — Edit. 
* Communicated by the Author. 



10 Mr. Potter on the Radii and Distance 

sures of the radii of the primary and secondary bows and their 
distance, as given by Sir Isaac Newton, with the resuks ob- 
tained from the theory, by using Frauenhofer's correct re- 
fractive indices. This comparison, which is detailed below, 
completely establishes the discovery that the ordinary rain- 
bows are not in the places hitherto asssigned to them. 

I had confirmed Sir Isaac Newton's measures in the year 
ISS^, by measures of the radii of the iris seen frequently in 
the mornings of autumn, in the dew-drops which float on the 
scum of stagnant ponds. These measures, although they had 
no claims to very great accuracy, were yet so nearly in ac- 
cordance with those of Sir Isaac Newton as to convince me 
that the wide discrepancies between the theoretical and ob- 
served radii could not possibly arise from errors of observa- 
tion ; and this I urged in a discussion at a meeting of the 
Cambridge Philosophical Society in the spring of 1836. 
Since then, the Astronomer Royal has deduced expressions 
on the undulatory theory of light, (see the May number of 
this journal, p. 452,) which indicate that the brightest parts of 
the bow ought to have their position different from those cal- 
culated from previous theories, and in the direction which 
the observed measures require; but he finds that the light 
shading away from the maximum of brightness, has at the 
old position a brightness which is about one half of that at 
the maximum, and which ought therefore to be distinctly 
seen : this is the point to be examined in order to test his ex- 
pressions. 

The general discovery that the bows are not in the posi- 
tions assigned to them hitherto, has been confirmed by mea- 
sures taken by Professor Miller in M. Babinet's experiment, 
in which the phaenomena analogous to those forming the rain- 
bows are viewed in a small cylindrical stream of water. 

Proceeding to discuss the observations, we find that Sir 
Isaac Newton's principal measurements were on the extreme 
radius of the primary bow and on the least distance between 
the two bows ; for after giving the results of his computations 
he says, " And such are the dimensions of the bows in the 
heavens found to be very nearly, when their colours appear 
strong and perfect. For once, by such means as I then had, 
I measured the greatest semidiameter of the interior iris, 
about 4-2 degrees, and the breadth of the red, yellow, and 
green in that iris 63 or 64 minutes, besides the outmost faint 
red observed by the brightness of the clouds, for which we may 
allow 3 or 4 minutes more. The breadth of the blue was about 
40 minutes more, besides the violet, which was so much ob- 
scured by the brightness of the clouds that I could not mea- 



of the Primart/ and Secondary Rainbows, 1 1 

surie its breadth." And again, " The least distance between 
this iris and the exterior iris was about 8 degrees and 30 mi- 
nutes." We see that the fundamental measures are for the 
extreme red of the primary bow, which has its utmost radius 
42° 4}', and the least distance between this and the correspond- 
ing part of the secondary bow = 8° 30'. Now, Sir Isaac 
Newton has taken ^ for the refractive index of this extreme 
visible red, which brings, as he says, the computations to agree 
nearly with the observations ; but from Frauenhofer's correct 
tables of refractive indices we find that it coincides very nearly 
with the letter D, or the middle of the orange. After all, — 
with this calculation for orange and measurement for extreme 
red, there is a discrepancy of no less than 14', for with re- 
fractive index = |, we have radius (if the sun were a point) 
= 42° 2', and adding sun's semidiameter =16' we have 
42° 18', diiFering 14' from the extreme measurement; the 
measured radius being less than the calculated one. 

Before we can proceed with the correct calculation we must 
fix on some refractive index as corresponding to the extreme 
visible red ; and the letter C being about the middle of the 
red, if we take about the letter B this will not be pushing the 
case too far, and will probably err in the favour of the old 
theory rather than otherwise. 

With this refractive index = 1*3309 we find for the radius 
of the primary bow, if the sun were a point, 42° 23', and add- 
ing sun's semidiameter, we have radius of extreme visible bow 
= 42° 39', and the difference between this and the observed 
quantity 42° 4' is 35', a quantity far beyond the limits of 
error of observation. 

The distance between the bows, however, shows the dis- 
crepancy in the strongest point of view, on account of its 
bearing so large a ratio to the whole distance. The above 
refractive index gives for the radius of the extreme red of 
the secondary bow 50° 20', and the difference between this 
and 42° 23' is 7° 57' ; subtracting from this the sun's semi- 
diameter for each bow, or 32' for both, we have 7° 25', whilst 
the observed distance is 8° 30', leaving a discrepancy of no 
less than 1° 5' in this small angle, which cannot possibly be 
attributed to faults in the measures. 

To test Mr. Airy's conclusions that the light at the position 
of the primary bow, according to the old theory, should be 
about one half of that at the brightest part if the sun were a 
point, and therefore distinctly bright in the real rainbow, we 
will allow a greater latitude in favour of the theory, and take 
the letter C refractive index = 1*33171 as belonging to the 
extreme Visible red ; this gives the radius of the primary bow 
42° 32', whilst the observed extreme bow has only a radius 



12 Lieut. Col. Emmett's Meteorological Observations 

42° 4', leaving a discrepancy of 26', or there is no visible 
light at that position indicated, instead of being of great 
brightness. 

Again, for the corresponding radius of the secondary bow 
we find 50° 17', and the difference between this and 42° 32' 
is 1° 45', so that according to Mr. Airy the light should be 
strongly visible to points distant 7° 45' from each other; whilst 
the utmost limit to which the light can be traced is still distant 
8° 30', and this difference leaves a strong presumption against 
the theory, and induces a corresponding argument in favour 
of the corpuscular theory, with which this fact is in ac- 
cordance. 



III. Meteorological Observations taken at St. George^s, Ber^ 
mudttf in the December half-year of IS"^*! ; introduced by Cor- 
rections of Observations for the June half-year. By Lieut- 
Col. Emmett, R.E.* 

MEAN height of barometer (Lond. & Edinb. Phil. Mag. 
Nov. 1837.) should be for July 30-069, and not 30-161, 
which is the height not corrected. The mean heights for Au- 
gust and September should each be reduced -020, '054 having 
accidentally been added for capillary action instead of '034. 

In the horary differences forwarded to Dr. Dalton it will be 
observed the numbers of observations at the different hours 
vary; they were also not always made on the same days: 
but in revising my journal I selected those days only for 9 a.m. 
and 4 p.m., on which the observations were made for both 
hours ; and upon that revision the tables in your January 
number were prepared. Such has been the course in the 
half-yearly observations now inclosed, completing the year 
1837. It is worth notice that the general fall of the baro- 
meter from 1 P.M. to 4 p.m. usually and considerably exceeds 
that from 9 a.m. to 1 p.m. Page 46, lines 4 and 5, should be 
subtracted from the " former," not the latter. 

From a frequent comparison of the dew-point directly taJcen 
with the wet-bulb thermometer I feel much confidence in it, 
where suspended in a large room free from currents and fully 
open to the air; but where exposed to currents, reflections from 
the ground, &c. it cannot be fully relied upon, both it and the 
register thermometer being affected thereby, and this it is often 
difficult to avoid. As I before stated, the difference between 
the wet and dry x by 2 and taken from the height of the dry, 
gives the dew-point nearly, but rather too low, as the multiple 
should be — 2 ; errors are therefore nearly doubled. 

* Communicated by the Author. 



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14- Meteorological Observations made at Bermuda, 
Horary Changes of Barometer. 



Months. 


No. of 
Observa- 
tions. 


9 A.M. 


4 P.M. 


Diff. 


Times 

higher 

at 4 than 

at 9. 


No. of 
Observa- 
tions. 


9 P.M. 


July. 


29 


30-121 


30113 


-008 


10 


28 


30-126 


August. 


29 


30-172 


30-156 


•016 


6 


25 


•171 


Sept. 


26 


30-185 


30153 


-032 


5 


19 


•171 


Oct. 


28 


30075 


30046 


•029 


4 


18 


•043 


Nov. 


29 


30-192 


30-167 


-035 


6 


10 


•048 


Dec. 


27 


30-075 


30-057 


•018 


8 


16. 


•093 




168 


30-137 


30113 


•024 


39 


116 


30-105 


June 
Half year. 


156 


•057 


•025 


•029 


27 


108 


-043 


Whole 
year. 


324 


30097 


30-069 


-027 


66 


224 


30-074 



Mem. — The observations at 9 a.m. and 4« p.m. were all 
taken on the same days ; the number of times when higher 
at 4 than at 9 a.m. are included in those of column 2. 

In August the barometer was lower at 5 p.m. '013 than at 
4< p.m. In September 4 p.m. gave the minimum, which 
continued so until near December, when 3 was at times 
lower than 4 p.m. 

Nine a.m. was almost always higher than 8 or 10. 

Winds. 



Months. 


N. 


N.E. 


E. 


S.E. 


s. 


s.w. 


w. 


NW. 


July. 


4 


2 


1 


6 


6 


45 


3 


26 


August. 


5 


8 


4 


16 


6 


20 


6 


28 
5 


Sept. 


4 


24 


6 


21 


6 


23 


1 


Oct. 


13 


26 


8 


16 


8 


10 


3 


9 


Nov. 


8 


23 


6 


10 


6 


27 


3 


7 


Dec. 


4 


24 


1 


7 


2 


10 


5 


40 




38 


107 


26 


76 


34 


135 


21 


115 


June half 
year. 


53 


70 


13 


50 


44 


126 


37 


145 


Whole 
year. 


91 


177 


39 


126 


78 


261 


58 


260 



Dr. G. Bird on the Nature and Properties of Albumen. 15 
Observations on the year 1837. 

Not Corrected 

corrected. and reduced to 32°. 

Barometer highest on 15th Feb.n q^./iqo o.cx.A.r.'i • 

Wind SE., light. Therm. 56° / ^^ ^^^ ^^ ^^^ 

Lowest 19th Jan. SE. heavy andj^ OQ'SQ^ 29*339 

suddenly changingtoNW. Th.61 J 

1-088 1-118 

Mean height corrected 30*053 

Deduct mean of vapour •54-2 

29-511 
Mean heat... 67'18 
Greatest...... 83-5 

Least 47* 

Observations on the last six months. 

Solar heat (greatest on blackened bulb therm.) 

July Aug. Sep. Oct. Nov. Dec. 
107° 115*> 103° 98° 89° 88° 

On the 14.th of November an aurora borealis was seen be- 
tween G and 7 p.m. centring on the north. Streamers ex- 
tending towards the Pleiades, and converging towards Cassio- 
peia, never rising so high. Stars, except of first magnitude, 
not seen through it. Colour, except streamers, a deep red. 
At its close, about 7 p.m., a haze covered the whole space, 
and there was lightning in the SW. Barom. 30-024. Therm. 
72°. Wind SW. fresh. During the appearance the gusts 
of wind were frequent and strong. 

The barometer had been gradually falling from the 10th, 
when it was 30-400; at 4 p.m. of the 14th it was down to 
29-998. 

Bermuda, March 31st, 1838. 

IV. Experimental Researches on the Nature and Properties of 
Albumen, S^c. By Golding Bird, M.D., F.L.S., G.S., ^c. 

Lecturer on Experimental Philosophy at Guy's Hospital.* 

N my former papers on this subjectf, I have given an ac- 
count of some of the properties of free and combined al- 
bumen, chiefly in relation to carbonic acid and electric currents ; 
and I hazarded a remark that these investigations would pro- 
bably serve to point out the presence of albumen in certain 

* Connnunicated by the Author. 

t [See Lond. and Edinb. Phil. Mag. vol. ix. p. 109.] 



I 



16 Dr. Golding Bird's Experimental Researches 

animal fluids in which its presence was unsuspected, and thus 
bring us acquainted with some new combinations of this im- 
portant product of organization : this remark has certainly 
received some support from the facts that have fallen under 
my notice during the last three years, and which I propose to 
detail in this paper. In the last number of the Guy's Hospitalre- 
ports, I have related such of my experiments as appeared to be 
connected with the physiological bearings of this subject, I shall 
therefore confine myself in this communication to the strictly 
chemical investigations, in the hope that they will assist in re- 
moving the obscurity hanging over that part of animal chemis- 
try connected with the peculiar and ill-defined organic princi- 
ples existing in mucus, saliva, &c., and stated by most chemical 
writers to differ from albumen in their chemical characters. 

1. Mr. Brande, in a paper published in the Philosophical 
Transactions for 1809, first demonstrated the existence of al- 
bumen in saliva and mucus, and it is a matter of regret that 
this philosopher has not followed up these views, as much light 
must have been thrown on this subject by researches guided 
by his talent. The state of combination in which the albumen 
existed in mucous fluids Mr. Brande failed to discover, 
although he remarked that in some features it resembled very 
closely an alkaline albuminate. Before giving an account of 
the results obtained by a repetition of his interesting experi- 
ments, it will be proper to describe the behaviour of those se- 
cretions, in which the presence of albumen was suspected, 
towards re-agents, as it will serve to bring us acquainted with 
a combination of albumen, differing from any described in my 
previous papers. For this purpose, saliva, or any other mucous 
fluid which does not coagulate by heat, may be taken as an 
example, and perhaps that viscid glairy fluid secreted during 
the first few days of acute bronchitis is the best for our pur- 
pose, as from its abundant secretion, and the frequency of the 
disease, it can be obtained in sufficient quantity for satisfactory 
chemical investigation. This form of mucus appears at first 
to be rather opake, from the presence of innumerable air- 
bubbles, but by repose in a cylindrical vessel these rise to the 
surface, and a nearly limpid fluid is obtained : this does not 
coagulate by heat, and presents the following appearances 
with re-agents : — 

A. On the addition of sulphuric acid a reddish-brown so- 
lution is formed ; which by dilution with water loses its colour, 
and becomes quite transparent. 

B. Nitric acid appears atjirst to coagulate it^ rendering it 
yellow in patches, and by the assistance of heat forms a pale 
yellow solution, becoming brown on the addition of an alkali. 



on the Nature and Properties of Albumen^ S^c. 17 

C. Hydrochloric acid removes the slight turbidity it pre- 
viously possessed, and causes it to assume a lilac tint. 

D. Ammonia, by the assistance of heat, partly dissolves it ; 
forming a gelatinous solution, becoming turbid when diluted 
with water. 

E. Acetic acid produces a partial coagulation ; causing the 
mucus to assume the appearance of a corrugated membrane, 
floating in the acid. 

F. Infusion of galls produces a copious precipitate. 

G. A quantity being evaporated to dryness, left a gum-like 
residue ; which, when carefully incinerated in a platinum cru- 
cible, yielded a perfectly white ash, destitute of all traces of 
iron : it turned turmeric paper brown, and partly dissolved 
in acids with effervescence, demonstrating the presence of an 
alkaline carbonate. 

Upon a review of these experiments, we find none of the 
phaenomena hostile to the opinion of the presence of albumen : 
indeed, some of them (B. C. F.) appear to indicate the pro- 
bability of its existence. The action of acetic acid (E.) is quite 
peculiar to that combination existing in mucus ; to which I 
shall again have occasion to refer. 

2. When nearly limpid mucus possessing the above pro- 
perties is kept for a few days exposed to the air, it becomes 
turbid, and gradually lets fall a white cream-like deposit. 
Some of this was collected and examined : it presented, under 
the microscope, the appearance of numerous round particles, 
which were readily recognised as coagulated or insoluble al- 
bumen ; for they dissolved in hydrochloric acid, yielding a fine 
lilac-coloured solution ; in nitric acid, with the aid of heat, 
they formed a yellow fluid, becoming brown on the addition 
of potass ; and with acetic acid they yielded a colourless so- 
lution, from which ferrocyanide of potassium threw down a pale 
yellow precipitate in the cold. 

3. Having thus proved this deposit to consist of albumen, a 
most interesting question arises as to its source; for, as has 
been already shown, (2) none of this principle could be ab- 
solutely p7'0ved to exist in the mucus before exposure to air, 
however much its presence might have been suspected. My 
first suspicions were, that the carbonic acid of the atmosphere 
had been the active agent, by combining with the substance 
which previously held the albumen in solution : this appeared 
to be probable, as some experiments, which it is unnecessary 
to detail, seemed to countenance the idea of the existence of 
albuminate of soda in mucus. I accordingly placed a glass 
filled with the same limpid mucus under a jar of hydrogen 

Phil. Mag. S. 3. Vol. 13. No. 79. July 1838 C 



18 Dr. Golding Bird's Experimental Researches 

gas, and in a few days the same creamy deposit appeared as 
when exposed to the free air ; lience proving satisfactorily, 
that the absorption of carbonic acid is not necessary for pro- 
ducing this curious change. 

4. When simple limpid mucus is boiled in a test tube, no 
coagulation, as already stated, takes place ; but on prolong- 
ing the ebullition, a milkiness appears, and after a few minutes 
an insoluble opake deposit ensues. This change is best ob- 
served by heating two or three ounces of the mucus over a lamp 
in a glass basin : the deposit is then more distinct, and by re- 
pose it becomes considerable. On examination, it is found to 
consist of albumen in amorphous particles, in which alone it 
differs from that precipitated from mucus by exposure to the 
air, or to an atmosphere of hydrogen. This change has been 
mentioned by Dr. Pearson *, although he did not examine the 
nature of the deposit. 

5. Another variety of mucous secretion, of frequent occur- 
rence, is that termed purulent or puriform mucus, secreted 
copiously during chronic bronchitis. This is generally very 
opake, often containing greenish masses, exceedingly tena- 
cious; so that on attempting to pour it from one vessel to 
another, instead of falling in drops, it forms one continuous 
rope, sometimes two or three feet in length, which is absolute- 
ly sectile. It usually contains innumerable air bubbles, which 
are evolved with difficulty : it can be scarcely said to be mis- 
cible with water, on account of its excessive tenacity. It bears 
considerable resemblance to simple mucus concentrated by 
evaporation, after having deposited part of its combined albu- 
men by exposure to air. The behaviour of purulent mu- 
cus with various reagents, therefore, exactly resembles what 
we should, a priori, expect from operating on simple mucus, 
holding numerous minute particles of insoluble albumen in in- 
timate diffusion. In general I have observed all the varieties 
of mucus to exert a faint but distinct alkaline reaction on sy- 
rup of violets, and on paper tinted with infusion of rose petals ; 
and after a few days' exposure to the air this effect becomes 
still more obvious. Dr. Babington has shown in a late paperf 
on this subject, that the bronchial mucus is constantly alka- 
line ; and my friend Mr. Richard Phillips lately informed me 
that he had been long aware of this circumstance, having de- 
monstrated it in the saliva by means of cudbear paper. 

6. The globules or particles of insoluble albumen present 
in puriform mucus are sufficiently obvious under a moderate 

* Philosophical Transactions, 1809, p. 322. 
t Guy's Hospital Reports, vol. ii. p. 539. 



on the Nature and Properties ofAlbumeti, S^c, 19 

magnifying power. When acted on by reagents the follow- 
ing were the results. 

A. Sulphuric acid formed a pale reddish solution with pu- 
rulent mucus; remaining nearly transparent, afterdilution with 
water. 

B. Nitric acid dissolved it with great difficulty, and not 
until after the application of heat : a pale yellow solution was 
then obtained, becoming orange red on the addition of a so- 
lution of potass. 

C. Ammonia by the assistance of heat yielded a turbid so- 
lution : when this was poured into cold water, it formed, after 
a few seconds' repose, a thin layer on the surface ; which, when 
viewed from above downwards, appeared quite diaphanous, but 
when placed horizontally between the eye and the light, ap- 
peared like a layer of semi-opake jelly : this after some time 
subsided in a manner closely resembling the subsidence of 
silicic acid from hydro-fluosilicic acid, after the addition of a 
potass- salt. 

D. Hydrochloric acid partly dissolves puriform mucus, 
forming a lilac-coloured trouble djluid. 

E. Acetic acid did not dissolve it, even after the application 
of heat : it appeared to contract the mucus into a corrugated 
membranoid mass, which floated on the surface of the fluid. 

F. By careful incineration in a platinum crucible, a nearly 
white ash was obtained, which exerted an alkaline action on 
turmeric paper, and partly dissolved with effervescence in dilute 
acids. It is unnecessary to make any remark upon these re- 
actions, as they resemble those produced by simple mucus, 
modified only by the presence of particles of free albumen. 

7. Some ounces of rather opake mucus of bronchitis were 
placed in a flask furnished vi^ith a tube bent twice at right 
angles, and immersed in lime water. A lamp heat was then 
applied to the flask ; and in a few minutes, long before actual 
ebullition, bubbles of gas were copiously evolved from the mu- 
cus ; and on passing through the lime water, they rendered 
it quite milky from a copious deposit of carbonate of lime; 
hence proving most satisfactorily the presence of carbonic 
acid in mucus, either free, or in so loose a state of combination 
as to be evolved by a very gentle heat. 

B. Two fluid ounces of similar mucus were mixed with a 
small quantity of a solution of potass, in a flask furnished as 
before with a bent tube, the end of which was immersed in a 
small quantity of pure dilute hydrochloric acid. On applying 
heat to the flask, the upper part and tube became soon filled 
with white fumes ; and after five minutes' boiling the lamp 
was removed : the dilute acid being carefully evaporated to 

C2 



20 Dr. Golding Bird's Experimental Researches 

dryness in a glass capsule, yielded numerous delicate feathers 
of hydrochlorate of ammonia. To obviate any source of fal- 
lacy in this experiment, some of the same specimen of diluted 
hydrochloric acid was evaporated to dryness ; but scarcely the 
minutest traces of residue were visible even with the aid of a 
lens. By simple distillation without admixture, mucus (as 
stated by Dr. Pearson) does not yield the smallest trace of 
ammonia ; hence we may very safely conclude, that although 
mucus does not contain free ammonia, yet it contains a salt of 
that base, most probably the chloride, (muriate of ammonia) 
a salt which the ingenious researches of Raspail* have proved 
to be almost universally present in animal fluids. 

8. Some fresh saliva, obtained without the use of any che- 
mical stimuli, was mixed with an equal bulk of water, and 
after violent agitation filtered ; this fluid was quite limpid, but 
by exposure to the atmosphere in an imperfectly closed jar 
during forty-eight hours, an opacity occurred precisely as in the 
case of mucus (2), the substance deposited not being soluble 
in nitric acid : the same thing occurred by exposure to an at- 
mosphere of hydrogen gas. Some of this limpid dilute saliva 
was exposed to heat in a glass tube ; no coagulation occurred : 
but by protracted ebullition in a glass basin numerous flocculi 
were deposited ; these flocculi could not be distinguished from 
coagulated albumen by their behaviour towards reagents. 

9. Some fresh human saliva was filtered, and exposed in a 
glass cup by means of copper wires to a current of electricity 
from a battery of six pairs of plates two inches square, excited 
by weak brine in the manner described in my last communi- 
cation on this subject (18) : coagulation ensued in a few seconds 
around the positive electrode; the coagulated mass adhered to 
the wire, and acquired a green tint from the oxidation of the 
copper electrode. Another portion of saliva was submitted 
to the electrolytic action of an electric current, in two cups 
connected by moistened cotton : coagulation very soon took 
place at the same electrode as in the last described experi- 
ment. 

10. Mucus diluted with water and filtered, presented the 
same appearances when acted on by a voltaic current as saliva, 
coagulation constantly taking place, and at the positive 
electrode. 

11. When the coagulated substance separated by electric 
action (9 and 10) from mucus or saliva was examined chemi- 
cally, in no single feature was it found to differ from ordinary 
coagulated albumen: in its solubility in acetic acid, alkalies, &c., 
not the slightest discrepancy could be detected. 

• Nouveau Systlvie de Chimie Organique, pp. 195, 346, &c* 



on the Nature and Pt'operttes ofAlhumenf Sfc. 21 

1 2. From all the foregoing experiments we learn, that fluids, 
as mucus and saliva, which do not give indications of the pr«- 
sence of albumen in a satisfactory manner by the application 
of ordinary reagents ( 1 and 6), by exposure to the air (2 and 8) 
or to an atmosphere of gaseous hydrogen (3, 8) let tall a de- 
posit in the form of minute particles, which resembles coagu- 
lated albumen so closely that we are hardly justified in con- 
sidering them as distinct. The same fluids when traversed 
by an electric current of low intensity (9, 10) give up, at the 
surface of the positive electrode, a white substance, which no 
chemical reagent to which it has been exposed can distinguish 
from artificially coagulated albumen. The results thus ob- 
tained by the action of electricity are corroborative of those 
obtained by Mr. Brande twenty-eight years previously, the 
only discrepancy that exists depending upon the surface at 
which the coagulation took place : to this I should beg to pro- 
pose a similar explanation to that which I have suggested in 
my former paper with regard to albumen (23). 

1 3. In consequence of the separation of coagulated albtimen? 
from saliva by an electric current, the existence of the pecidiar 
animal matter of saliva (ptyalin of Berzelius) might appear 
questionable, and it appeared probable that it might be some 
albuminous combination instead of a distinct proximate prin- 
ciple. To determine this, some ptyaliji was prepared by 
evaporating some saliva to dryness, digesting the residue in 
hot alcohol, and then in cold alcohol acidulated with acetic 
acid. The insoluble residue, which notwithstanding its wash- 
ing with alcohol was acid, partly dissolved in water, leaving 
an insoluble substance very closely resembling, if not iden- 
tical with, coagulated albumen. The watery solution con- 
tains, according to Berzelius, {Traite^ v. 6.) tolerably pure 
ptyalin. This solution was placed in two glass cups con- 
nected by moistened cotton, and exposed by means of platina 
wires to the action of an electric current from 36 pairs of 
plates two inches square excited by weak brine : coagulation 
ensiled at both electrodes^ most freely at the negative side. 
This coagulated substance could not be distinguished from 
albumen, hence it appeared probable that the ptyalin of Ber- 
zelius consisted of some hitherto unknown combination of 
that principle. 

As it is obvious that no previously known combination of 
albumen would present all the phaenomena of the (so called) 
peculiar proximate principles of mucus or saliva with reagents, 
although its solutions in alkalies and in carbonic acid would 
present some, it became a most interesting inquiry to seek 
after and develop the nature of this unknown combination. 



$9 Prof. Johnston on the Composition of certain 

This was a task of no slight difficulty, on account of our very 
limited acquaintance with the nature and properties of the al- 
buminous combinations found in the different secretions. 
[To be continued.] 

V. ' On the Composition 'of certain Mifieral Substances of 
Organic Origin. By James F. W. Johnston, M.A., F.R.SS. 
L. Sf E.y F.G.S.f Professor of Chemistry and Mineralogy, 
Durham."^ 

V. Elastic Bitumen of Derbyshire. 

THE elastic bitumens of Derbyshire and Montrelais have 

been analysed by Henry jun. He found them to con- 
sist of 

From Odin Mine. From Montrelais. 

Carbon 52-250 58*260 

Hydrogen... 7*496 4*890 

Nitrogen ... 0*154 0*104 

Oxygen 40*100 36*746 



100* 100* 

Journal de Chimie Medicale, i. p. 18. 

This analysis is open to two remarks; first, on the excessive, 
and in the present state of manipulation the almost impossible, 
refinement of estimating one tenth of a per centage of nitro- 
gen; and second, on the large amount of oxygen which it 
indicates. This quantity is so much beyond what we should 
expect from the appearance of the substance itself, from its 
chemical relations, and from the circumstances under which 
it is met with, as at once to awaken doubts of the accuracy 
of the analysis. 

I have analysed three varieties of the elastic bitumen of 
Derbyshire, and have obtained a widely different result. 

1 . The first was soft, elastic, adhering to the fingers, yield- 
ing to slight pressure, of a brown colour and a strong pe- 
culiar odour. At 212° Fahr. it decreased in weight, giving 
off" a volatile matter possessing the unpleasant odour of the 
mass. 

10*052 grs. burned with oxide of copper gave 31*07 grs. 
of carbonic acid, and 12*01 8 grs. of water. These are equal to 

Carbon 85*474 

Hydrogen 13*283 



98*757 
Communicated by the Author. 



Minerals of Organic Origin. No. V. Elastic Bitumen, 23 

The loss may either be due to the presence of oxygen, or 
to the extraction of a trace of the more volatile part when 
heated, before burning, for the purpose of pumping out the 
water. 

2. The second, of which I had a larger supply, had a close 
resemblance to moderately soft India rubber. Its colour was 
of a darker brown. Boiled in water its colour became paler, 
but it again darkened on drying at 212°. During the boiling 
a more volatile portion collected on the surface of the water 
and the sides of the flask, which on cooling presented the ap- 
pearance of a very soft white, or slightly brownish solid. At 
212° in the air it also diminished in weight. Boiling alcohol 
and aether extracted from it a similar volatile substance, but 
very sparingly, and of a browner colour. I did not recognise 
in this substance the bitter taste remarked by M. Henry. I 
have in my possession, however, a substance of a similar kind 
from South America, which I shall describe in a future Num- 
ber, possessed of an intensely bitter taste, a trace of which 
may, perhaps, be occasionally present in the elastic bitu- 
men, and give a bitterness to the matter extracted from it by 
aether. 

Of this second or harder variety, 13*66 grs., cut into small 
pieces and boiled once in aether and three times in alcohol, 
lost 2*46, or 1 8*008 per cent. It still retained its elasticity 
after this treatment. 

Of the portion thus boiled, 11*195 grs. gave on burning 
34*165 grs. of carbonic acid, and 12*67 grs. of water. Of a 
second portion, first boiled for a long time in water, and af- 
terwards in successive portions of alcohol, as long as any- 
thing seemed to be taken up, 8*74 grs. gave 26*447 of car- 
bonic acid, and 9*86 of water. These are equivalent to 

1st. 2nd. 

Carbon 84*385 83*671 

Hydrogen 12*576 12-535 



96*961 96*206 

And indicate the presence of from three to four per cent, of 
oxygen in the portion of the bitumen which remains after the 
action of alcohol and aether. 

3. The soft elastic bitumen is said by long keeping to be- 
come hard and brittle. It is certain that portions of this 
brittle kind occasionally occur imbedded in the softer mass. 

Of a specimen of this brittle variety having a vitreous 
lustre and conchoidal fracture, 

a. 6-263 grs. gave 19*47 carbonic acid, and 6*957 of water. 

b. 5*93 grs. gave 18*48 6*63 



24) Prof. Johnston on the Composition of certain Minerals. 

These are equivalent to 

Ist. 2nd. 

Carbon = 85-958 86-177 

Hydrogen = 12-3'1.2 12-423 



98-300 98-600 

It would appear that this variety also contains a small 
quantity of oxygen. 

These analyses show us, 

1. That the elastic bitumens are very nearly akin to the 
Hatchetine and Ozocerite, and are probably an equiatomic 
carbohydrogen (CH) slightly altered. 

2. The first compared with the succeeding analyses shows 
that in the soluble and more volatile of the two portions of 
which these bitumens consist, the carbon and hydrogen are 
more nearly in atomic proportion than in the elastic insoluble 
portion, and render it probable that the soluble part is a 
variety of Hatchetine or Ozocerite, of which originally the 
entire mass consisted ; and therefore, 

3. That the change which the originally pure carbohydro- 
gen has undergone, has either been the result of a decompo- 
sition analogous to that which many of this group of carbo- 
hydrogens are known to undergo, or of an oxidation to a 
small extent, perhaps of both. If oxidized it may either be 
so by the direct addition of oxygen to the unchanged com- 
pound, or by the replacement of a portion of its hydrogen, 
in which case the atomic ratio of the fundamental elements 
must be altered. Were we certain that the second variety 
analysed was wholly free from mixture, the ratio of its ele- 
ments might be calculated and the true nature of the change 
determined; while doubt remains in regard to its purity, 
however, the result of such a calculation would be deserving 
of little confidence. 

In regard to the origin of this substance, I am inclined to 
attribute its presence in the mineral veins and fissures which 
traverse the mountain limestone in Derbyshire, to sublimation 
from beneath. The immense stratiform deposits of trap which 
traverse that district, indicate a sufficient cause for such 
sublimations. The contact of a fused lava with the organic 
matters which abound in the strata of the carboniferous aera, 
could not fail to cause the evolution of volatile substances, which 
would condense when they reached a colder region. Bitu- 
minous substances are found also in the carboniferous lime- 
stone in Fifeshire, where trap rocks are known to penetrate or 
disturb the strata; and it is not unlikely that in most cases 
their appearance near the surface is due to a high temperature, 



On the Separation of the Oxalic from other Organic Acids. 25 

derived from some similar source, acting on substances either 
themselves organized, or like coal of organic origin. 
Durham, May 1838. 

VI. On the Separation of the Oxalic from other Organic Acids. 
By James F. W. Johnston, M.A., F.R.SS., L. ^ E. 
F.G.S., Professor of Chemistry and Mineralogy, Durham.* 

\ T the Liverpool meeting of the British Association in 
-^ September last, I exhibited and stated the composition 
of a beautiful salt I had formed some months before, consist- 
ing of an atom of nitrate with an atom of oxalate of lead and 
two atoms of water. In the Number of the Philosophical 
Magazine for May is given an extract of a paper by M. De- 
jardin, in which this salt is very correctly described, and cer- 
tainly without the knowledge of my having previously made 
it known f. As the study of this interesting compound, how- 
ever, has suggested an easy method of separating the oxalic 
from other organic acids, I shall briefly describe the unpub- 
lished observations I have made upon it. 

I prepare the salt by adding nitric acid in considerable 
quantity to a weak solution of oxalic acid, or of acetate of 
lead, and pouring in slowly a solution of subacetate of lead, 
or of dilute oxalic acid. Shining plates of the compound 
speedily begin to fall. If the quantity of oxalic acid be mi- 
nute, or if it be largely diluted, the crystals fall only after 
some time, and in the form of six-sided tables, of which two 
of the sides are longer than the others, possessing a silvery 
whiteness and peai'ly lustre, and striated longitudinally so as 
to exhibit the most beautiful prismatic colours when light is 
reflected from them. I have also obtained it in acicular prisms 
nearly an inch in length, which according to the measurement 
ofProfessor Miller of Cambridge, are oblique rhombic prisms. 

Decomposed by sulphuretted hydrogen it gives a colourless 
solution, which, when evaporated, emits fumes of nitric and 
yields crystals of oxalic acid. 

Heated to 212° this salt does not diminish in weight; at a 
temperature of about 500° Fahr. it loses 2 atoms (5*425 per 
cent.) of water, and before it reaches 570° Fahr. it has given 
off copious red fumes, lost upwards of 19 per cent., and is 

* Communicated by the Author. 

t I may take this opportunity of mentioning, that under the name of 
lodal, M. L'Aniy has lately described a compound of which I published 
an account in the Edinburgh Journal of Science (II. p. 415.) some years 
ago. It is obtained by the action of nitric acid on iodine in alcohol, and 
has not yet been analysed. 



26 Prof. Johnston on the Separation of the 

wholly converted into carbonate of lead. At a higher tem- 
perature the carbonic acid is driven off. 

Water decomposes it, extracting when boiled over the salt 
the greater part of the nitrate, and leaving nearly pure oxa- 
late; a small portion of the double salt being dissolved at the 
same time, which precipitates again on cooling. Thus 24f*26 
grs. boiled in water left 12'70 grs. of insoluble residue, or 
52'35 per cent. ; the quantity of oxalate in the salt being only 
50'016 per cent. When newly precipitated, or before it has 
been dried at 212°, it is much more readily decomposed, so 
that it cannot be washed on the filter even with dilute nitric 
acid without decomposition. 

10*59 grs. heated to nearly 500 Fahr. lost before any trace 
of red fumes appeared 0*56 = 5*28 per cent, of water. Three 
successive portions on heating to redness left respectively 
67*51, 67*55, and a purer variety 67*28 per cent, of oxide of 
lead. 

These results agree with the formula PIN + PIC + 2 HO. 

Exper. Calcul. 

Or, Oxide of lead 67*28 67*312 

Acids 37*54. 37*263 

Water 5*28 5*425 



100* 100* 

I met with this salt in the course of an examination of the 
action of nitric acid on certain organic substances. Thus if 
oil of turpentine or of lemons, the balsams, the sugars, colo- 
phony, elemi, gamboge and other resins. Burgundy pitch, 
or indigo be boiled in nitric acid, either dilute or concentrated, 
and to the acid solution, from which the yellow resin formed 
during the operation has been precipitated by water, sub- 
nitrate of lead be added, the new salt falls in great abundance, 
indicating the production of oxalic acid. Not suspecting the 
crystals I obtained in this way to be a double salt, I was at 
much pains in making out their elementary composition by 
burning with oxide of copper, and I only prepared it directly 
from a mixture of oxalic and nitric acids after I had completely 
analysed it. During the action of nitric acid, however, on 
some, if not upon all the organic substances above mentioned, 
other acids are formed ; and this is more especially known to 
be the case in regard to indigo. These acids are held in so- 
lution along with the oxalic, and continue to be so held after 
the addition of subacetate of lead to the acid liquid ceases to 
throw down any more of the double salt. It becomes inter- 
esting then to examine how far the whole of the oxalic acid 



Oxalic from other Organic Acids, 27 

could be thrown down by this means while the solution still 
remained acid. 

1. If into solutions of acetic, tartaric, citric, carbazotic, 
indigotic, benzoic, succinic, gallic, meconic, pyromeconic, 
mucic, or camphoric acids, nitric acid be poured and after- 
wards subacetate of lead, or if nitric acid be added largely 
to solutions of acetate or nitrate of lead and solutions of these 
acids be dropped in, the precipitate at first formed speedily 
redissolves, and no further precipitate, crystalline or other- 
wise, appears on standing for any length of time. I have not 
tried any other organic acids, but the same is probably 
true of many of them also. 

2. But if into a solution thus prepared, and containing al- 
ready one or more of these acids, a few drops of a solution of 
oxalic acid be introduced, crystals of the double salt begin to 
appear. 

3. This is beautifully illustrated, and at the same time the 
conversion of tartaric into oxalic acid, by dissolving the former 
or the bitartrate of potash in dilute nitric acid; the solution 
gives no precipitate with subacetate of lead, but boil it a little, 
and a precipitate in shining crystals appears on adding the 
salt of lead. This forms a very instructive class experiment. 
Care must be taken to have the solution sufficiently acid, or 
more or less of pure oxalate of lead will accompany the double 
salt. 

4. 15*92 grs. of tartaric and 6*08 grs. of oxalic acid with 

one atom of water (C + H) were dissolved in a small quantity 

of water, and poured into an acid concentrated solution of 
nitrate of lead in large excess. The double salt collected 
and dried at 212° Fahr. weighed 45*03 grs., equivalent to 

6*14 grs. of (C+H). This indicates 0*06 of oxalic acid in 
excess, an error which can hardly be avoided, from the im- 
possibility of sufficiently washing the precipitate and filter 
without risking decomposition. 

5. But the oxalic acid may also be separated from all these 
other acids, and estimated with tolerable precision, without the 
formation of the double salt. Thus 10 grs. of oxalic acid in 

crystals (C + 3 H), equivalent to 5*73 of anhydrous acid, were 
mixed with 20 of tartaric acid, 10 of citric, 2 of benzoic, 4 of 
succinic, and an unmeasured quantity of acetic acid dissolved 
in two ounces of distilled water, and acid nitrate of lead added 
to the solution. By this method of proceeding a sufficient 
quantity of nitric acid was present to prevent the tartrate, 



28 Prof. Hare on the Reaction of the Essential Oils 

benzoate, &c. from falling, but not enough to cause the for- 
mation of the double salt. A crystalline precipitate, indeed, 
fell, but it was only oxalate, with a few flakes of the double 
salt. After drying at 212 it weighed 23*16 grs. and lost when 
heated to redness 26*85 per cent. Pure dry oxalate contains 
24'*68 per cent, of acid; and 28*16 grs. of oxalate are equiva- 
lent to o'71 of anhydrous acid, very nearly the quantity em- 
ployed. Some time must be allowed for the perfect deposition 
of the whole of the oxalate or of its double salt. 

From these experiments it appears that by simply acidify- 
ing strongly with nitric acid, the oxalic may be separated 
almost completely from solutions containing any of the other 
organic acids above enumerated, and its quantity determined 
with considerable accuracy. 

The utility of this process in separating the oxalic acid, 
formed so largely in the preparation of the indigotic and 
carbazotic acids and other highly oxidized compounds, need 
not be pointed out, nor the means it affords us of estimating 
quantitatively the nature of the changes produced on organized 
bodies by the action of oxidizing agents. 

Durham, May 29, 1838. 

VII. Of the Reaction of the Essential Oils "isoith Sulphurous 
Acid, as evolved in union with jSither in the Process of 
jEtherificationy or otherwise. By R. Hake, M.D., Professor 
of Chemistry in the University of Pennsylvania'^. 

IITAVING mixed and subjected to distillation two ounces 
^-*^ of oil of turpentine, four ounces of alcohol and eight 
ounces of sulphuric acid, a yellow liquid came over, having 
all the appearance of that which is obtained in the process 
for making oil of wine, described in a preceding article. 
On removing, by means of ammonia, the sulphurous acid ex- 
isting in the liquid, and driving off the aether by heat, a liquid 
remained, which differed from oil of turpentine in taste and 
smell, although a resemblance might still be traced. This 
liquid was without any sensible action on potassium, which 
continued bright in it for many weeks. It proved, on ex- 
amination, to contain a small quantity of sulphuric acid. I 
ascertained, afterwards, that in order to produce these results, 
it was sufficient to pour oil of turpentine on the mass which 
remains after the termination of the ordinary operation for 
obtaining aether, and apply heat. Subsequently it was ob- 
served that when the sulphurous aether was removed by heat 

• From the Transactions of the American Philosophical Society, N.S. 
vol, v. 



isoith Sulphurous Acid, SfC. 29 

or evaporation, without the use of the ammonia, the pro- 
portion of sulphuric acid in the remaining oil was much 
greater. 

By subjecting to the same process several essential oils, I 
succeeded in obtaining as many liquids to which the above re- 
marks were equally applicable. With some of the oils, how- 
ever, similar results were, by this method, either totally or 
partially unattainable, in consequence of their reaction with the 
sulphuric acid being so energetic as to cause their decompo- 
sition before any distillation could take place. No product 
can be obtained by distillation with sulphuric acid and al- 
cohol from the oil of cinnamon obtained from cassia. From 
the oils of sassafras and cloves, but little can be procured. 

However, in one instance, by previously mixing the oil of 
sassafras with the alcohol, in the manner described in the ac- 
count given of the first experiment with the oil of turpentine, 
I succeeded in obtaining in addition to a small quantity of the 
heavy liquid containing sulphuric acid, a minute quantity of 
a lighter one, devoid of that acid, which burned without 
smoke, was insoluble in water, and very fluid. I am disposed 
to consider the liquid thus procured as a hydrate of sassafras 
oil, or sassafreine, as I would call it, being analogous to hy- 
dric aether. 

The oil of sassafras, whether isolated or in combination, 
possesses a remarkable property, which, I believe, has not at- 
tracted sufficient observation: I mean that of producing an 
intense crimson colour, when added, even in a very minute 
quantity, to concentrated sulphuric acid. 

One drop of oil of sassafras imparted a striking colour to 
forty-eight ounce measures of sulphuric acid, and appeared 
perceptible when it formed less than a five millionth part. 
This property was completely retained by the lighter liquid 
above described as procured from oil of sassafras. 

I subsequently observed, that when sulphurous acid, whether 
in the form of sulphurous aether, in that of a gas, or when in 
union with water, was brought into contact with any of the 
essential oils (including kreosote), which were subjected to 
the experiment, they acquired a yellow colour, and a strong 
smell of this acid. 

In the case of the yellow compound thus obtained from 
any of the essential oils which I have tried, if the sulphurous 
acid be removed by heat, the oil, by analysis, will be found 
to yield sulphuric acid. That some acid of sulphur remains 
in union must be evident, since washing with ammonia will 
not entirely remove the power of yielding sulphuric acid ; and 
the total absence of the sulphurous smell demonstrates that 



so Prof. Hare on the Reaction of the Essential Oils 

the sulphurous acid either enters into an intimate combination 
with the oil, or acquires oxygen sufficient to convert it into 
sulphuric or hyposulphuric acid. 

Those essential oils which contain oxygen, are most affected 
by the action of sulphurous acid. 

Both the oils of cloves and cinnamon, after admixture with 
sulphurous aether and subsequent distillation, gave, on ana- 
lysis, precipitates of sulphate of barytes. In the case of 
cloves, the precipitate amounted to one-seventh of the whole 
weight. 

By distilling camphor with alcohol and sulphuric acid, I 
obtained a yellow liquid, which, by washing with ammonia 
and evaporation, in order to get rid of the sulphurous aether, 
yielded an oil. The oil, by standing, separated into two 
portions, one solid, the other liquid. The solid portion re- 
sembled camphor somewhat in smell, but differed from it by 
melting at a much lower temperature, becoming completely 
fluid at 175°. 

I found that the essential oils of cinnamon and cloves pos- 
sessed an antiseptic power, quite equal to that of kreosote, 
and that their aqueous solutions, when sulphated, were even 
superior to similar solutions of that agent. 

One part of milk mingled with four parts of a saturated 
aqueous solution of the sulphated oil of cloves, remained after 
five days sweet and liquid, while another portion of the same 
milk became curdled and sour within twenty-four hours. 
Having on the 2nd day of July added two drops of oil of cin- 
namon to an ounce measure of fresh milk, it remained liquid 
on the 1 1th; and, though it finally coagulated, it continued 
free from bad taste or smell till September, although other 
portions of the same milk had become putrid. A half ounce 
of milk, to which a drop of sulphurous oil of turpentine had 
been added, remained free from coagulation at the end of two 
days, while another portion, containing five drops of pure oil 
of turpentine, became curdled and sour on the next day. 

A number of pieces of meat were exposed in small wine 
glasses, with water impregnated with solutions of the various 
essential oils. Their antiseptic power seemed to be in the 
ratio of their acridity. The milder oils seemed to have com- 
paratively little antiseptic power, unless associated with 
the sulphurous acid, which has long been known as an anti- 
septic. 

In cutaneous diseases, and, perhaps, in the case of some 
ulcers, the employment of the sulphurous sulphated oils may 
be advantageous. 

A respectable physician was of opinion that the sulphurous 



tsoith Sulphurous Acid, 8fc. SI 

sulphate of turpentine had a beneficial influence in the case 
of an obstinate tetter. 

Possibly the presence of sulphurous acid may increase the 
power of oil of turpentine as an anthelmintic. 

Pieces of corned meat hung up, after being bathed with an 
alcoholic solution of the sulphurous sulphated oil of turpen- 
tine, or with solutions of the sulphated oils of cloves or cin- 
namon, remained free from putridity at the end of several 
months. That imbued with cinnamon had a slight odour and 
taste of the oil. 

I am led, therefore, to the impression that the antiseptic 
power is not peculiar to kreosote, but belongs to other acrid 
oils and principles, and especially to the oils of cinnamon and 
cloves. 

The union of sulphuric acid with these oils appears to ren- 
der them more soluble in water : whether any important 
change is effected in their medical qualities by the presence 
of the acid may be a question worthy of attention. 
' I have stated my reasons for considering the ammoniacal 
liquid, resulting from the ablution of the aethereal sulphurous 
sulphate of aetherine with ammonia, as partially composed of 
hyposulphuric acid. By adding to this ammoniacal liquid a 
quantity of sulphuric acid, sufficient to produce a strong 
odour of sulphurous acid, and then a portion of any of the 
essential oils ; a combination ensued, as already described, 
between the oils and the sulphurous acid liberated by the sul- 
phuric acid, so as to render them yellow and suffocating. 
The habitudes of cinnamon oil from cassia under these cir- 
cumstances were peculiar. A quantity of it was dissolved, 
communicating to the liquid a reddish hue. The solution 
being evaporated, a gummy translucent reddish mass was 
obtained, which, by solution in alcohol, precipitated a quan- 
tity of salt, and being boiled nearly to dryness, redissolved 
in water and again evaporated, was resolved into a mass 
having the friability, consistency, and translucency of common 
rosin ; but with a higher and more lively reddish colour. Its 
odour recalls, but faintly, that of cinnamon ; its taste is bitter 
and disagreeable, yet recalling that of the oil from which it 
is derived. Its aqueous solution does not redden litmus ; nor, 
when acidulated with nitric acid, does it yield a precipitate 
with nitrate of barytes. 

Of this substance ten grains were exposed to the process 
above mentioned, for the detection of sulphuric acid, and 
were found to yield a precipitate of Q'6 grains of sulphate of 
barytes. 

It may be worth while to mention, that in boiling the sul- 



32 Mr. C. HoltzapfFel on a Scale of Geometrical Equivalents 

phated oils with nitric acid, compounds are formed finally, 
which resist the further action of the acid, and are only to be 
decomposed by the assistance of a nitrate and deflagration. 
I conjecture that these compounds will be found to merit 
classification as aethers formed by an oxacid of nitrogen. 

One of my pupils, in examining one of the compounds 
thus generated, was, as he conceived, seriously affected by it, 
suffering next day as from an over dose of opium. He also 
conceived that a cat, to which a small quantity was given, 
was affected in like manner. 

I had prepared an apparatus with the view of analysing 
accurately the various compounds above described or alluded 
to, by burning them in oxygen gas ; when, by an enduring 
illness of my assistant, and subsequently my own indisposi- 
tion, I was prevented from executing my intentions. 



VIII. On a Scale of Geometrical Equivalents for Engineering 
and other Purposes. By Mr. Charles Holtzapffex-, 
Associate of the Institution of Civil Engineers. 

To the Editors of the Philosophical Magazine and Journal. 
Gentlemen, 
T^HE scale of geometrical equivalents is a particular com- 
■*- bination of several of the scales of equal parts, which 
I have recently contrived and explained*: by means of this 
instrument, with the aid of a little arithmetic, a great variety 
of tedious calculations in constructive science generally, but 
more especially in engineering, may be performed with con- 
siderable correctness, by the simple inspection of scales, pro- 
portionals to the quantities under observation. 

As regards drawing, the scales are shown to be only an 
extension and generalization of the common application of 
reduced scales of 1, 2, 3, &c. inches to the foot; and in their 
application to numbers or quantity, they are laid side by side 
with their zeros in contact, after the manner of thermometer 
scales, two of which are frequently engraved on the same in- 
strument for comparison, so that we may read the height of 
the mercury either by the centigrade scale, freezing being 
called zero, and boiling 100; or by the Fahrenheit scale in 
common use in this country, the same space being divided 
into 180 degrees, freezing being then marked 32. We may 
thus transpose the French reading of the instrument into the 
English, or the reverse. 

I have extended this latter application of scales to many 

♦ A new System of Scales of Equal Parts, by C Holtzapfi'el. 



for lEitigineering and other Purposes. 



33 



kinds of quantity, amongst others to the various measures 
and weights, as the linear measures, the cubic measures and 
measures of capacity, the superficial measures, and the weights 
of all denominations and all countries, any two of a kind ad- 
mitting of comparison after the manner explained with the 
thermometer. The scales intended for drawing are gradu- 
ated on separate slips of card, in order that they may be im- 
mediately applied to the drawing and to curves without the 
intervention of compasses, and at the same time the confusion 
arising from crowding together several lines of graduations 
on the same slip of wood or metal to avoid expense, is got 
rid of. 

Card has been selected as the material from its economy, 
its flexibility, the distinctness of the black lines (ruled upon 
them in my new dividing engine,), the facility of writing or 
printing upon the card the titles and explanations, &c., but 
principally from the identity of material of the paper scales, 
and of the drawing paper, they are in consequence affected 
in the like degree by atmospheric influence, which has been 
experimentally proved*. The different series are ruled on 
cards of light colours for distinction. 

The purpose of the present instrument, however, being dif- 
ferent, the card is glued on a thin mahogany board six inches 
wide, so as to contain on one or both sides several lines of 
graduations, beginning from one line or zero; and any two of 
the scales may be readily compared, or the correspondence 



\ 



INDEX 



/I 

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 n I 



^A.CUBIC'^^DS\ JiiiimTrriiiiiii 



11 /t" I \ all 

TTTi 1 1 1 1 1 1 1 I |-ijTTT7B. CuBic Febt, \ y 1 1 [ 1 1 1 1 1 1 1 j I [ 1 1 1 j 

6 

~i 1 1 l|I 1 I i I I ) 



1 1 1 1 1 1 1 1 1 1 r trrVrrry C.GoBlC LVCHES | 



50 000 U 

N 1 1 1 1 1 1 1 iri 1 1 1 1 M i/D. Spherical Ins.// i i i i i i i i rrnrri'rr 
i I / ' 1 I I 

100 O OP X ^ .^ „ x,XT A'ooo 



rprjTjTjnrjTjTp \rf\mz'^. S UPER^.Yabds V' 1 ' I ' I ' I M ' 1 ' I ' 



l|l)l],llllllljimi|I^F.Sl7PER^EBETi 



=y G.SuPER^lNrCHE& 




• A New System, &c., pp. 1 — 9, and 43. 
Phil. Mag. S.S. Vol. 13. No. 79. July 1838. 



D 



S* Mr. C. Holtzapffel on a Scale of Geometrical Equivalent 

of the whole series may be observed at one view, by the as- 
sistance of a particular kind of square represented in the 
wood-cut. It consists of two slips of card, connected at the 
upper and lower edges by two slips of wood glued between 
them, so as to make a kind of slider or ferrule. 

The first idea was to cut the edge of the card square; but 
a better mode subsequently suggested itself, namely, to draw 
a line across the index, and then to serrate the edge, so that 
the several parts of the line might serve for the more accurate 
appreciation and subdivision of the graduations by the eye. 
At the same time, the card index receives the titles of the 
scales A, B, C, &c. and there is therefore no necessity to dis- 
tress the eye by running continually to the end of the instru- 
ment to ascertain the same, as the index gives all the parti- 
culars called for, in immediate contiguity. 

The 20 lines of graduations selected for one side of the 
present instrument are arranged as follows : 

A. Cubic yards 

B. Cubic feet 
, C. Cubic inches 

D. Spherical inches 



:> Cubic measures. 



E. Superficial yards 

F. Superficial feet 

G. Superficial inches 
H. Circular inches 

I. Imperial gallons 
J. Bushels 
K. Barrels 
L. Tuns 

M. Pounds troy 

N. Pounds avoirdupois 

O. Cwts. 

P. Tuns 



T Areas and columns, 
one foot high 
or deep. 






Measures of 
capacity. 



Weights estimated 
in water. 



Q. French lineal metres "^ 

R. French cubic metres I French metrical 

S. French super^ metres [ system. 

T. French kilogrammes. J 
All these scales are graduated to one common standard, 
namely, the unit described in the pamphlet*, one tenth of an 
inch English representing one cubic foot English : all the 
others are multiples and submultiples, proportionate to the 
values of the several measures. 



* P. 31. 



for Engineering and other Purposes. 35 

The line B, therefore, the basis of the instrument, is a line 
of inches and tenths, marked 10, 20, 30, &c. Now as the 
cubic yard contains ^7 cubic feet, the unit of the line A is 
B X 27 or 2*7 inches decimally subdivided. 

The line C for cubic inches is so proportioned that 1728 
of its nominal divisions, (the number of cubic inches con- 
tained in one cubic foot,) are equivalent to one tenth of an 
inch ; but as we could not graduate such a scale, nor employ 
it when done, our purpose is equally well served by the nu- 
merals annexed to the divisions. 

Ten inches denotes 100 cubic feet on B, that space must 
also denote 1728x100 or 172,800 cubic inches on C, 10 
inches is therefore divided into 17 great divisions, numbered 
respectively 10,000, 2, 3, 4, 50,000, 6, 7, 8, 9, 100,000, and 
so on, each fifth numerical being the true number of cubic 
inches, the ciphers being omitted in the intermediate places to 
avoid confusion. 

The line D for spherical inches is C multiplied by "5236 
the constant multiplier for giving the value of the sphere en- 
closed in any given cube, or as expressed at the end of the 
scale itself C x '5236 = 3'030. In this simple manner all the 
values are worked out and graduated, the formula for con- 
structing each being marked at the terminations of the several 
lines. 

It only remains to observe that the group for superficial 
measures is calculated for areas and columns of the common 
height of one foot; the group for weights, which refer to 
water, from the cubic foot of water weighing 62*5 pounds 
avoirdupois, therefore 10 inches represents 6250 pounds avoir- 
dupois ; the group for measures of capacity, from the gallon 
being equivalent to 10 pounds of water, and so on. 

The scales of the instrument being therefore proportionals as explained, 
we may read off in groups the value of any one measure in any other: 
it is desired, for example, to know all the equivalent values of 33 cubic 
feet, expressed upon the scale, (see diagram). Set the index to 33 on B. 
cubic feet, and at one view the several answers appear, namely, on A. 
1-22 cubic yards, on B. 33 cubic feet, on C. 67,000 cubic inches, (the 
cube root of which from the tables or 38 to 39 will be the side in inches 
of an equal cube,) on D. we read 1 09,000 spherical inches, (the cube root 
of which 48 nearly is the diameter in inches of a sphere containing 33 
cubic feet,) on E. 3-67 square yards, on F. 33 square feet, on G. 4750 
square inches, (each area being supposed to be the base of a column one 
foot high, and the square root of any of these will give the side of an 
equal square column of the same height); on H. we read 6050 circular 
inches, the square root of which is the diameter in inches of a circular 
column or cylinder one foot high, (also containing 33 cubic feet) on I. 206 
gallons, on J. 25*75 bushels, on K. 5*72 barrels, on L, -818 liquid tuns, 
on M. 2500 pounds troy, that being the weight of 33 cubic feet of water, 

D 2 



36 Mr. C. Holtzapffel on a Scale of Geometrical Equivalents 

on N. 2060 pounds avoirdupois, (multiplying either of these by the spe- 
cific gravity of any substance, gives the weight of each, or it may be done 
by inspection of the scales provided for that purpose p. 24 — 30,) on O. we 
read 18'4 cwts., on P. 'OS tuns, on R. '932 cubic metres, on S. 3'06 super- 
ficial mUres, as before extending to the height of one foot, and finally on 
T. 932 kilogi-amvies, as the weight of 33 English cubic feet of water. 

It is not at all likely that the whole of these comparative 
values would be wanted in any one inquiry, but all the mea- 
sures are of frequent occurrence in calculations. To render 
the reading as simple as possible the numerals denote the 
true values throughout, so that no reductions nor changes 
have to be made, unless it be the calling 1, either 10, 100,1000, 
&c. which is common to all decimal scales : it need scarcely 
be said that when the value of any one scale is thus altered, 
the same must be done with all employed at the same time. 
It will be found the most convenient first to take down the 
numbers denoted on the scale, and then to seek the true place 
for the decimal point. 

The results given in the general example show the varied 
nature of the transpositions which the scale effects : these need 
not be extended by way of illustration ; but we may also read 
and resolve decimals, and perform many of the calculations 
in engineering, &c. which would otherwise require the employ- 
ment of two or more constant multipliers. 

Required the value of the decimal -231 of a cubic foot, in cubic inches. 
Employ B. and C. The answer is 399*2 inches. 

Convert the decimal '987 of a pound troy into the decimal of a kilo- 
gramme. Employ N. and T. The answer is -3685. 

"What fraction of a liquid tun of water is 7^ cwts. of the same ? Employ 

0. and L. Answer -322. 

The diameter of a sphere of water containing 500 gallons? Seek 500 in 

1. and take the cube root of the number obtained in D (from the tables). 
Answer 263,900, the cube root of which is 64 inches nearly. . 

Required the side of an equal cube. Read 64 the diameter of the given 
sphere in D, and the answer 33'5 will be found in C ; the two lines C. 
and D. performing the multiplication and division by '5236. 

And in the like manner the lines G. and H. effect the multiplication 
and division by '7854. Required the diameter of a column 45 feet high to 
contain 790 gallons. Divide the quantity by the height in feet for the 
contents of one foot, for which height the scales are calculated; answer 
] 7'55 gallons : seek that number in I. and take the square root of the 
number found in H., namely, 51 5-4, as the answer, or squared, 23 inches 
nearly, as the diameter of the column. 

Required the contents of a cooling floor for a brewery 19 yards long by 
20 yards wide, covered to the depth of 9 inches, in cubic feet, barrels, and 
tuns avoirdupois. By arithmetic 19x20 = 380, the area of the floor in 
square yards ; deduct ^th, 9 inches being |^ths of 1 foot, for which depth 
the scales are calculated, 380 less ^th = 285. 

Seek 285 in E. and read the answers in B. 2565 cubic feet, in K. 445*^ 
barrels, and in P. 71 '56 tuns. 

Required further how many times this quantity would be required to 



fw Engineering and other Purposes. 37 

fill a vat 30 feet diameter and 40 feet liigh, and also the pressure i gainst 
the side of the vat at the bottom, and ] 0, 20, and 30 feet below the sur- 
face. To find the contents of the vat square the diameter, and multiply 
it by the depth, (by arithmetic) 30x30x40 = 36,000. Seek 36,000 in 
H. and the contents will appear 28,280 in G. (Thus the scales G. and 
H. although representing inches in the general scheme, have given the 
product of 36,000x7854 = 28,280 cubic feet.) Seek 28,280 in B. the 
proper scale for cubic feet, and the answers 4910 barrels will be found in 
K. and 701 liquid tuns in L. 

It only remains to divide the entire contents of the vat 28,280 by 
the contents of the floor 2565, the quotient 1 1 nearly will be seen on 
inspection as the number of brewings required. 

To find the pressure against the bottom of the vat, &c. seek the depths 
40, 30, 20, and 10, in G, and the pressures will be read respectively in M. 
17"4, 13*1, 8'7, 4-35 pounds avoirdupois. 

The scales on the other side of the instrument are for the 
quadratic and cubic relations of quantities. 

Scales are made up of two parts, the spaces which are geo- 
metrical quantities or extents, and the numerals which are 
arithmetical quantities. So likewise do they admit of two 
modes of application, first to the measurement of spaces by 
means of their spaces, as in making reduced and enlarged 
drawings, -proportional spaces being then marked by equal 
numerals; — and secondly, to the measurement of numbers, as 
in the slide rule, the thermometer scales, &c., proportional 
numbers in this case being marked by equal spaces. 

This will be rendered very clear by an example. Required 
I of a line A B, and | of the number 8. Select two scales in 
the proportion of the terms of the fraction, namely, 

012345678 



A b B 



The spaces of the three scale are each three tenths of an inch, 
and those in the four scale four tenths. 

The line A B equals 3 spaces of the denominator scale, but 
the three spaces of the numerator scale A b are only | of 
A B, A B being divided into 4 parts on the three scale ; 
therefore in drawing, we measure the object with the denomi- 
nator scale, and we draw from corresponding numbers on the 
numerator. But if we desire to know |ths of 8, we find that 
as regards the numerals on the scales matters are reversed, 
the greater spaces require fewer figures in the same extent, or 
they are numerically of smaller value; therefore to read | of 
8 by the above scales, we seek the given number in the nu- 
merator, and we find the reply 6 over against it on the de- 
nominator scale. 



38 Mr. C. HoltzapfFel 07i a Scale of Geometrical Equivalents 

The above application of scales is true of all ratios ex- 
pressed as vulgar fractions, decimal or others, as |, .y., S^-^., 
^•|36^ T-lff' ^^ being essential the scales should be 7 and 8, 

11 and 9, 28 and 4 2-236 and 1-414 times any 

unit, and that they are employed as explained. The three 
first fractions are comprehended in the scales prepared for 
lines or drawings, which are 1, 2, 3, 4 to '■25 inches long, si- 
milarly divided and figured*. As we obtain from them all 
the distinct proportions that may be expressed as vulgar 
fractions in terms not exceeding 25, (which are given in the 
pamphlet both as fractions and decimals, and arranged in the 
order of magnitude) they offer great facility for making re- 
duced or enlarged copies of drawings, models, &c. after va- 
rious manners, many examples being given, and they likewise 
serve for working numerical ratios of simple proportion. The 
two latter or the decimal fractions would result from the em- 
ployment, after the same manner, of two other series of scales 
for the areas of superficies and the contents of solids, the units 
of which are respectively the square and cube roots of the 
numbers 1 to 10. 

These may need a little more explanation. Required |ths 
the size of a given area A B C D. 

" The parallelogram A B C D is divided into 9 equal and 
proportional parallelograms, by the 
division of each of its sides into 
three parts. If, however, we wnly 
reckon two parts each way, we find 
them to include but four out of the 
nine equal areas. The square root 
of 4 is 2, and the square root of 9 is 
3, therefore the areas being as 4 to 9, the sides are as 2 or 3, 
or as the square roots of the former, which was to be shown. 
This would be equally true if the scales were applied in the 
inverse order, and of any two ; also if the figures were com- 
plex ; for a semicircle, or equilateral triangle on A B, would 
have for the new diameter or side A E, and so with every 
part of which the figure might be made up." 

The scales for solids admit of the same explanation. 

There are 24 lines of graduations on the other face of the 
scale, (or it is somewhat more convenient to have them as 
two distinct instruments,) namely, the scales for areas y^, 1, 
2, 3, 4, 5, 6, 7, 8, 9, 10 and 100, and the same number for 
solids. The first and last are for those cases in which the 
ratio of enlargement or diminution cannot be expressed in 
fractions not exceeding 10 in either term, which will be re- 
ferred to hereafter. 

* A New System, &c. pp. 16—23. 




for Engineering and other Purposes. 



S9 




From the name selected for the instrument, namely, the 
scale for geometrical equivalents, it may be seen it is princi- 
pally designed for the alteration of known forms and quan- 
tities; it therefore remains to show this application to any 
solid of known contents, in any ratio, and in any prescribed 
manner. 

1. When one dimension only is altered, it will be in the 
direct proportion of the ratio, the original figure being con- 
sidered as unity. 

2. When two dimensions are altered, it will be in the du- 
plicate ratio of the two, or as the square root of the ratio. 

3. When all three dimensions are altered, it will be in the 
triplicate ratio of the sides, or as the cube root of the ratio. 

For example, a given vessel measures 6 feet long, 4 feet wide, and 
3 deep, its contents are therefore 6 X 4 X 3 = 72 cubic 
feet. Required the dimensions of other vessels to con- 
tain 180 cubic feet, according to each of the modes. The 
new vessels will be to the original or unity as 180 to 72 
or '^J> times the size, which reduced to its lowest terms 
is ^ or 2| times as great. 

1. To enlarge the one dimension only, say the depth, multiply it by 
the ratio |, 3xf = Ih, the measure of the new depth, ^ ^ 
and 6x4x7'5 »= 180, the new contents. 

2. A new vessel to be of the same depth, but to have 
its area enlarged 2^ times. The new sides will be found 
by multiplying the given sides by the square root of the 

ratio, or V I or f !f|-| ; this by any of the modes of 
arithmetic, or by logarithms, would take some time; 
whereas by the scales, the 5 quadratic scale having for 
its unit 2-236 inches, and the 2 scale 1'4142 inches, 
(the square roots of 5 and 2,) they represent the above fraction, and the 
application is precisely the same as seeking |ths of 8 already explained : 
set the index to 6, the given side on the numerator scale 5, and the new 
side is found in the denominator scale 2, namely, 9*48 ; and do the same 
for the other side 4 feet, which comes out 6'32. 
I have never taken the trouble to obtain these 
quantities otherwise, and the multiplication of 
the 3 sides one into the other gives the new con- 
tents, 1 79*74, whereas it ought really to be 180, 
so that the error only amounts to ^ about the 
720th part of the whole quantity. 

3. The vessel to contain 21 times as much as 
the given one 6x4x3, enlarged in each of its di- 
mensions, will be found by multiplying each of the sides by the cube root 
of the ratio, or V f- Therefore, seek 6, 5, 3 in 
the 5 cubic scale, and the new sides will appear 
respectively over against them in the denomina- 
tor scale 2, namely, 8"16, 5*43, 4*08, which multi- 
plied into one another for the new contents give 
180-779, about the 240th part too much, a result 
sufficiently near for most practical cases. 

Of course, what is true of the two scales em- 









40 Mr. C. HoltzapfFel on a Scale of Geometrical Equivalents 

ployed, will be true of any two, and the method is applicable to all solids, 
of all forms and sections. It is desired to increase the contents of a pan 

or vessel 2.J times, the same as explained for the cu- ; 

bical vessel. Draw several ordinates across the figure. In 

1. The vessel being altered in height only, the 
diameters remaining constant, increase the distance 
between the ordinates 2^ times, whence the second 
form immediately beneath would result. 

2. The figure being altered in diameter, the depth 
remaining constant, the lengths of the ordinates must 

be increased v | times by the quadratic scales : the 

new figure would be of , — ■ . 

this form. -^-_ _ ; - -^ 

3. The three dimen- 
sions being altered, the 
space between the ordi- 
nates, as well as their 

lengths, must be multiplied by Vf by means of the 
cubic scales 5 and 2; this new figure would be produced, or a copy of the 
original in the same proportions as to height and 
diameter as the original : and further, should it 
be desired to mix the two modes, that is to alter 
both the general contents, and one of the mea- 
sures in any defined ratio, for example, to make 
a new vessel as before containing 2^ times as 
much, but of only half the height, we must thus 
learn the ratio. Half the height with the same diameters would give half 
the contents ; the increase of the 
diameters by the quadratic scales 
must therefore be doubled by 
employing the quadratic scale f , i X f being equal to 5 the ratio re- 
quired for the new contents. 

We have therefore complete command over the capacity of 
all vessels, under all proportions of general contents, and 
specific variations of form. The truth of this method admits 
of rigid demonstration, if we consider the ordinates to divide 
the figure into so many zones, or as regards the section into 
trapezoids and rectangles, and that the curved line running 
through them is superseded by short right lines. Of course, 
the more ordinates that are used the more nearly true will 
be the result. The circle would by this treatment become 
an ellipse, which may be taken as a further proof of the cor- 
rectness of the result, as to find the area of an ellipse the two 
diameters are multiplied into each other, and the product by 
•7854- 

When vessels of complex form are constructed as retorts, 
boilers, pans, stills, tanks, &c. it would be desirable to retain 
drawings of them, with the several measures written upon 
them, and also a memorandum of the cubic contents obtained 
either by calculation or experiment, as by means of the scales 
these data may be employed for obtaining the new contents, 



Jor Engineering and other Purposes. 



41 



and dimensions of similar vessels, under all varieties of size 
and form with considerable accuracy, whereas the complexity 
of such calculations often cause them to be neglected, leaving 
the results to the unassisted judgement, or in other words to 
be guessed at. 

The scale of geometric equivalents being, as before ad- 
verted to, rather an instrument for transposition, than calcu- 
lation in the strict sense of the word, it will be found desi- 
rable to estimate the dimensions of certain known forms of 



given areas for reference 



a few have been tabulated. 





Containing 

100 

Superficial 

Feet. 


Containing 

1000 
Superficial 

Feet. 


Diameter of a circle. . . : . . 


11-284 


35-682 


Side of a square 


10- 


31-623 


Side of a hexagon 


6-204 


19-619 


Side of an octagon 

Side of a decagon 


4-551 
3-605 


14-392 
11-400 


Side of a dodecagon 


2-989 


9-451 



They would be employed in the following manner : 
Required the diameter of a circular gasometer to contain 60,000 cubic 
feet when filled to the height of 20 feet. 1000 cubic feet would be con- 
tained in a circle 35-68 feet diameter, 1 foot high ; the height being 20 feet, 
would necessarily contain 20,000 feet, therefore the proportion would be 

2l)'.'ooo °'' ^ T' ^^^^ 35-68, the given diameter in the 3 quadratic scale, 
and the new quantity 61-9 will be found in the denominator scale. 

Required the side of a hexagonal tank to contain 3600 cubic feet when 
filled 5 feet high. The side of a hexagon containing 100 feet is 6-2, the 
ratio is therefore '^f^^ or y/I-x6-2 = 16-45 : this quantity obtained from 
the quadratic scales 7 and 1 would be one 35th too small, and might be 
corrected to that amount by a second process if required; and if in the like 
manner it were required to multiply any quantity by the factor ^, we 
might arrive at the result at twice as ^ x f = j^ > and so on. 

It will, however, be found in general the most convenient 
to bring the ratio within the series of fractions expressed by 
the numbers 1 to 10, beginning with y^th, and ending with 
LP, or ten times, which are tabulated ; but we may take cog- 
nizance of ratios very much larger and smaller after the fol- 
lowing manner. 

"We may employ any two terms indifferently provided they 
are in the same proportion ; for example, the terms 1 and 
2, — 2 and 4, — 3 and 6, — 4 and 8, are each as one to two : their 
squares are 1 and 4, — 4 and 16, — 9 and 36, — 16 and 64, or 
as 1 to 4 throughout; it follows therefore that -^^ being the 
tenth part of 1, the 20th part of 2, the 30th of 3, and so on, 



42 Mr. C. Holtzapffel on a Scale of Geometrical Equivalents 

we obtain the proportion 10, 20, 30, 40 times, or J^, ^V, 
^1^, ^'^th part by the joint employment of the y'^th and the 
1, 2, 3, 4 scales, &c. 

Again, the square root of 100 is 10, of 200, 14'142, of 
300, 17*320, or ten times the square roots of 1, 2, 3; we may 
.therefore call these scales 100, 200, 300, by simply multi- 
plying the numerals by 10, so that to obtain ^/^^^ of any 
quantity, seek it in 9, and the answer in 7, which, supposing 
it to be 5*314, must be read 53*14; and lastly, y'^j being the 
thousandth part of 100, by employing the Y\jth line on the 
one hand, and the 1, 2, 3, 4, 5 lines, (multiplied by 10,) on 
the other, we obtain the -^y^, ^-^fS>^ Woo' ^^^ ^° °"* these 
matters are, however, of great simplicity to those at all ac-^ 
customed to the employment of decimals. 

An example will better explain the utility of this arrange- 
ment. 

A mine 650 feet deep has to be drained by means of a pump 17 inches 
diameter : required first the total contents of the entire column of water in 
cubic feet, gallons and tuns weight, and also the pressure on each square 
inch of the column ; and the requisite diameter of a steam cylinder, work- 
ing under the effective pressure of 12 pounds on the inch which shall ba- 
lance the column in the mine. 

17 the diameter of the pump or column squared and multiplied by the 
depth or 17*x650 = 187850, seek that number in G. (square inches) and 
read in B. 1304 cubic feet, in I. 8140 gallons, and in L. 3231 tons avoir- 
dupois, as the contents of the entire column. 

For the pressure on each square inch of the pump, seek the depth 650 
feet in G, and against it 282*5 will be found in M. The pressure per inch 
on the pump cylinder being 282-5 pounds, and the proposed effective press- 
ure of the steam being 12 pounds per inch, the ratio in which the cyHnder 
should be altered is f/y^^. 

The required result, and the others presented at the same view, are ex- 
tracted in three columns : the first column shows the real titles of the 
quadratic scales, — the second the assumed titles, or the former multiplied 
by 3 (300 being nearest to 282-5,) ; and the third column the diameters of 
the equivalent cylinders under each different pressure, the given diameter 
of the pump having been sought in the 300 column. 

Scales 100, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. 
Pressures 300, 3, 6. 9, 12, 15, 18, 21, 24, 27, 30. 
Diameters 17, 170, 121. 98, 85, 76, 70, 64, 60, 57, 54. 

The nearest whole numbers having been taken. The truth of this will be 
apparent 17'x300 being 86700, and 852 x 12 being likewise 86700. 

But as a comprehensive example, suppose it is desired to 
enlarge the drawings of a steam-engine, the new one to be as 
5 to 4. 

The contents of all the vessels, as the cylinder, condenser, 
air-pumj), &,c. will be increased by the cubic scales 5 and 4. 

The areas of the valves, passages, pipes, and the compli- 



for Engineering and other Purposes. 43 

cated surface of the internal flues or fire surface of the boiler, 
by the quadratic scales 5 and 4. 

The new and old cylinders being in simple height as 15 to 
14, the lengths of the beam, rods, arms, &c. would be ex- 
tended by the scales for lines 15 and 14, and so on. If the 
proportions of the vessels were altered, the application of the 
scales would be modified as already shown by the diagrams. 

This paper might have been easily extended by other ex- 
amples of many kinds, but I trust that enough has been said 
to explain the principle and general method employed, that 
alone being required in this place. 

The scale of geometrical equivalents in some respects re- 
sembles the slide rule, but it possesses certain advantages. 

1st. It is easier to graduate scales of equal parts than those 
in which the divisions are unequal. 

2nd. It is easier to subdivide equal divisions by the eye than 
unequal ones, and they admit of the employment of the ver- 
nier if required. 

Srd. The results are obtained in groups, whereas each se- 
parate question requires a distinct setting with the slide rule. 

4th. In using the slide rule we are subject to two sources 
of error, imperfect setting as to the gauge-point, and imper- 
fect reading off' in the quantities. From the construction of 
the scale of equivalents, as the scales all begin from one com- 
mon line, the setting can never be disturbed. It is therefore 
only liable to the single error of reading off', the settings being 
constant. 

5th. In order to obtain the most accurate results it is occa- 
sionally desirable to double or halve the quantities, so as to 
get as far from the zero of the scales as possible, whereby the 
error of reading will be proportionably diminished. The 
very nature of the slide rule limits this application, as some- 
times only a third part or less of the scales remain in contact. 

6th. But the most serious drawback to the slide rule is the 
constant practice that is required for using it with facility, 
arising principally from the difficulty of assigning the true 
value to the answers, whether units, tens, hundreds, thousands, 
&c., and the constant reference to the tables of the gauge- 
points. 

Now, as in all cases the true values are expressed upon the 
scales of the new instrument, and their particular names de- 
note at the same time the functions and relationships of the 
several scales, both inconveniences are in a great degree, if 
not entirely, obviated. 

7th. It is true, the slide rule may be employed for any arbi- 
trary setting, whereas the present instrument is in a measure 



44) Mr. Laming ow the primaty Forces of Electricity. 

limited to certain constant multipliers ; but tlie combined re- 
sult of some three or four of these are sometimes concerned 
in giving a single solution on the scale of geometric equiva- 
lents, and that in a novel and curious manner. 

The multipliers selected possess an extensive range, and 
include the elements of most of the calculations likely to be 
called for ; the mode to be pursued can scarcely be mistaken, 
as the simple names of the functions serve to indicate the 
proceeding in each case; and when a little arithmetic and 
the tables of squares and cubes are brought in to assist, the 
powers of the contrivance are exceedingly increased. We 
exchange the tediousness of calculation and the errors which 
creep in, notwithstanding every care, for the certainty of the 
relations of the lines; subject however to the error of read- 
ing, which will not in general be found an inadmissible quan- 
tity; it rarely equals the one hundredth part of the totals, 
and is sometimes within the thousandth part of the same. 
The answers given in this paper were obtained from the 
instrument alone: their proof by calculation, (in which the 
formulae on the scales will assist,) will show the degree of 
reliance that may be placed on the method. 

Of course such scales might be adapted to a variety of other 
investigations, and they would be made to any given data. 

In order to lessen the expense of the present instrument, I 
propose to graduate the scales on copper-plate* and to print 
from them. 1 should therefore feel obliged by any suggestions 
calculated to improve the arrangement proposed previously 
to so doing. 

I remain. Sir, your most obedient servant, 

64, Charing Cross, London, C. Holtzapffel. 

June 6th 1838. 

IX. On the primarij Forces of Electricity. By Richard , 
Laming, Esq., M.R.C.S. 

[Continued from p. 498.] 

32. \irE may now apply the principle of compensation to 
' ' some of the leading phaenomena attendant on the ac- 
cumulation of free electricity in rarified air. As the quantities 
susceptible of being accumulated in conductors under atmo- 
spheric compensation have been shown, both theoretically 
and experimentally, to vary in the simple ratio of the density 
of the air, the quantity that is communicable firom one body 

•As explained in the pamphlet, the error of contraction after printing is 
immaterial with the proportional scales; it is only inadmissible in such as 
demand an agreement with the standard measure, pp. 6 and 7. 



Mr. Laming o?i the primary Forces of Eleclricity. 4t5 

in plenum, to another supposed to be insulated in an absolute 
vacuum^ is equal to nothing. 

33. From this it evidently follows, first, that when a con- 
ductor containing a plus charge be partly inclosed in a re- 
ceiver, and the air within the latter is gradually withdrawn, 
the free electricity will progressively recede to those parts of 
the conductor which are external to the receiver; for by the 
theory the several parts of a conductor can never differ in 
intensity (28.); which in this case they would do unless the 
charge requiring compensation, and the air by which it is 
compensated {both within the receiver) diminished in the same 
ratio. 

34'. In the second place we learn that by reducing the 
density of the air when a charged conductor is insulated 
wholly within the receiver, we virtually increase the quantity 
of electricity to be compensated by an assumed unit of air; 
thus causing the force of attraction between that electricity 
and its compensator to be increased. Now the intensities 
being as the square of the quantities directly, and the quan- 
tities virtually as the densities of the air directly, the electrical 
intensity of any given chiarge is as the square of the atmo- 
spherical density inversely ; and this is the conclusion Mr. 
Harris has arrived at by experimenting in various ways*. 

35. We are thus enabled to understand why a conducting 
body highly charged and insulated under a receiver gradually 
becomes discharged as the vacuum becomes more perfect ; a 
fact which has been long known, but until now never ex- 
plained. It is usual to ascribe it to diminished resistance by 
the atmospheric air ; but the phaenomenon may be made to 
take place equally when the pressure remains undiminished ; 
which has been proved by first abstracting part of the air 
from a receiver and then heating the residuum ; under such 
circumstances it was found that, however the temperature, 
and with it of course the pressure, might be changed, so long 
as the quantity of free electricity remained constant, its inten- 
sity varied as the square of the density or quantity of the air, 
inverselyf. 

36. The phaenomena which characterize the deflection of 
the pith-balls, straws, gold-leaves, or other moveable parts of 
diverging electroscopes, are rendered intelligible by the ap- 
plication of our principles. Suppose the compensation of a 
plus body B, free to move, to devolve entirely on two other 
uninsulated fixed bodies, A A', placed on either side and at 
equal distances from it ; B will have an equal tendency to 

* Phil. Trans. 1834, part ii. 

t Ibid., p. 228. 



46 Mr. Laming on the primary Forces of Electricity. 

move in two directions, and consequently remain stationary ; 
now if B be divided into two parts in a plane at right angles 
to a right line passing through the axis of A A', the two parts 
will instantly separate. 

37. Just so it is in experiment; two balls, for instance, 
charged with free electricity and in contact, are virtually 
one conductor; compensated, when freely insulated in the 
atmosphere, solely by the air. While the two balls are in 
contact the compensating atmosphere of neither can be per- 
fect spheres ; and hence it must extend to a greater distance 
from the surface than if it wholly surrounded each of the 
bodies individually; and as by Coulomb's law the force of 
attraction is much greater as the distance is less, the distant 
particles of compensating air will be brought near to the at- 
tracting surfaces, and thus by intervening between the balls 
separate them from each other. 

38. Coulomb has ascertained by experiment that the force 
with which two bodies equally charged,^ thus apparently repel 
one another, varies as the square of the distance inversely; 
which is quite in accordance with the principles we are ex- 
amining ; for before two bodies can come together the inter- 
vening air must be removed, and this we have shown to be 
held against each body with a force varying as the square of 
the distance inversely ; hence the apparent repulsion of two 
such bodies will be equal to the sura of the individual forces 
in each body, but this addition leaves the ratio unaffected. 

39. In the preceding case the charges of the two balls be- 
ing equal their compensating atmospheres were of the same 
extent; but we may so dispose the free electricity on two balls 
that their charges shall be unequal, and then the radii of their 
compensating atmospheres will differ also. Under such cir- 
cumstances of course the law of Coulomb will not express the 
apparent repulsion at all the distances ; this theoretical conclu- 
sion Mr. Harris has arrived at by the induction of a series of 
nice experiments made with his very ingenious bifile balance*. 

40. But the influence of the major attraction in causing 
the divergenceof an electroscope has always to encounter a 
retarding force in the reaction of the instrument ; and however 
minute this latter force may be, it must occasion the two com- 
pensating atmospheres in some measure to intersect one an- 
other ; with this in recollection we shall easily perceive that 
one of two charged balls may have so much of its free elec- 
tricity abstracted as to enter zVs^^ within the compensating 
atmosphere of its associate, in which event of course instead 

* Phil. Trans. 1836. p. 430 et seq. 



Mr. Laming on the primary Forces of Electricity. 47 

of receding from each other, the two balls will, as shown by 
Mr. Harris, be brought together*. 

41. We may next inquire into the sufficiency of the new 
theory to explain the various circumstances under which dis- 
charges of free electricity may be made to take place between 
plus conductors and their compensating bodies. 

As action and re-action are in all cases equal, it is evident 
that the minus common matter in a negatively electrical body 
must as forcibly attract the free electricity in a plus body as 
it is itself attracted by it ; and therefore were the cases parallel 
in other respects also, the phaenomena of electrical attraction 
and electrical discharges would at all times be simultaneous. 

42. In the case of electrical attractions we certainly have 
a retarding force in the gravity of one or both of the at- 
tracted bodies, and frequently in the gravity of materials to 
which they are attached; and this retarding force may be 
sufficiently great to overcome the attractive force at any di- 
stance, however small. On the other hand, either one or 
both of the attracted bodies may be so free to move as to op- 
pose a retarding force indefinitely minute ; and then they will 
be brought together through a distance almost, though never 
quite, so great as that through which under the circumstances 
their compensating influence extends. 

43. Now unless there were a retarding force to electrical 
discharges, these would occur at the extreme distance at which 
the major attraction acts, or in other words, at which com- 
pensation becomes established ; and thus the discharging di- 
stances being greater than the distances at which visible at- 
traction is effected, the latter phsenomenon never could take 
place. It is obvious therefore that electrical discharges are 
restrained by some retarding force ; and this is supplied in 
the minor attraction acting between the free electricity in the 
plus body, and the electrical equivalent which is natural 
to it. 

44. Since then the minor electrical attraction in every plus 
conductor is a retarding force to the discharge of its free 
electricity, it will act with less effect upon any particular elec- 
trical atom as it is further removed from the general mass ; 
and therefore a plus charge may be drawn off with a less 
amount of major attraction, and consequently at greater di- 
stances, from projecting points and angles than from any 
other surfaces. Hence the great freedom with which elec- 
tricity issues from a point to its compensating atmosphere; 
and hence also the escape of the electrical spark towards a 
conductor, at greater distances through the compensating at- 

• Phil. Trans. 1836, p. 431. 



♦8 Mr. Laming oti the primary Forces of Electricity. 

mosphere as the part of the charged body to which the con- 
ductor is presented is smaller and more prominent. 

45. The form of the conductor, or of that part of a con- 
ductor from which the phis charge is to be abstracted, being 
given, then if an unit of quantity of free electricity be re- 
tarded in it by an unit of minor force, two units of quantity 
should be retarded by two units of force, three quantities by 
three units of force; the retarding force thus continually in- 
creasing in the simple ratio of the quantities of free electri- 
city. Consequently the discharging distances from any given 
surface should vary in the same ratio ; for, as we have already 
seen, (10) the intensity of abstracting, or major force being 
constant, the distances at which it acts var}' in this ratio. 

That this is the ratio observed by electrical discharges un- 
der all circumstances may be proved by an appeal to facts ; 
and I think the proof will be received as an additional evi- 
dence of the minor electrical force. 

46. Electrical discharges, as they occur between conductors 
compensated in the open atmosphere, have been examined 
by Mr. Harris ; whose experiments on the subject decide most 
unequivocably, that under such circumstances at least, and 
whether the conductors be connected with Leyden surfaces 
or not, " the quantities of electricity requisite to produce a 
discharge vary with the distances directly*." 

47. Mr. Harris has also ascertained with his usual accuracy, 
that in a rarified atmosphere " the distances through which a 
given accumulation could discharge, varied in an inverse simple 
ratio of the density of the air. Thus in air of one half the 
density the discharge occurred at twice the distance f." Now 
by reducing the density of a compensating atmosphere to one 
half, we virtually double the charge to be compensated by the 
residuum ; in this case also we therefore see that the dis- 
charging distances are as the quantities of free electricity. 

48. The same acute philosopher has further proved, by a 
very ingenious and exact mode of experimenting, that pro- 
vided the densities or quantities of air in a receiver remain 
unchanged, the temperatures may take a very wide range with- 
out affecting the discharging distance of a given accumulation 
of free electricity; in this case again the discharging distances 
are therefore as the quantities of free electricity. 

49. The very great distances at which electrical discharges 
may be made to take place in vessels nearly exhausted of air 
has induced a general belief that, in the language of Dr. Ure, 
*' electricity is confined to the surface of bodies by a species 

* Phil. Trans. 1834, p. 225. f Ibvi., p. 229. 



Mr. Liming on the primary Forces of Electricity. 49 

of mechanical pressure which air exercises." In the valuable 
magazine of facts to which I have found occasion so frequently 
to refer, there is enough said to carry with it a conviction 
that Mr. Harris is by no means satisfied of the truth of the 
supposition ; indeed he has in one place actually proved that 
the resistance to electrical discharges does 7iot vary as the 
atmospheric pressure ; it would appear however that he is 
unconscious of his achievement ; for in other places we find 
him insisting on the opposite conclusion as the legitimate in- 
duction of his experiments generally. 

50. The proof to which I allude is furnished by a series of 
experiments, in which the temperature of a given quantity oj 
air inclosed in a receiver was made to vary between 50 and 
300 degrees of Fahrenheit, without " in the least " affecting 
the discharging distances of the electrical accumulations ; 
notwithstanding the atmospheric pressure at different times 
of course differed enormously*. In these experiments, as in 
all the preceding, the discharging distances were as the quan- 
tities of compensating air, and therefore by our principles as 
the quantities of free electricity ; that is to say, as the abstract- 
ing force minus the retarding force of the minor electrical 
attraction. 

51. I have made many experiments on the discharging di- 
stances of free electricity in receivers filled with rarified air, 
without finding anything which offers the least evidence of 
electricity being retained on the surface of bodies by reason of 
atmospheric pressure ; but on the contrary every evidence 
which the investigation was capable of affording has been ob- 
tained in favour of the principles generally on which this theory 
is based. For instance, let the density of the air, or its press- 
ure, have been what it may, the discharging distances have 
invariably increased in the simple ratio of the quantities, until 
the sides of the receiver and the external air have by their 
comparative proximity interfered with the ratio by assuming 
part of the compensation of the charge. 

In the following experiments, which are adduced as ex- 
amples of such an interference, the quantities of electricity 
were estimated by the unit jar; the discharges were made 
between two brass balls Ifths of an inch in diameter, placed 
in the axis of a receiver, more or less exhausted, about 4^ 
inches in diameter and IS inches high ; and the balls commu- 
nicated, respectively, with the opposite conductors of a Ley- 
den jar exposing about two square feet of coating. 

* Phil. Trans. 1834, p. 229, 230. 
PMl. Mag, S. 3. Vol. 13. No. 79. July 183S. E 



50 Mr. Laming on the primary Forces of Electricity, 

Table F. 

Discharging Comparative Same by Cal- 

Distances in Inches. Quantities. culation. 

I 35 

§ 70 70 

I 106 105 

J 140 140 

I 174 175 

f 199 210 

Table G. 

Discharging Comparative Same by Cal- 

Distances in Inches. Quantities. culation. 

■ J 12 

I 24 24 

f 36 36 

J 48 48 

I 60 60 

I 71 72 

I 77 84 

1 81 96 

1^ 86 108 

If 92 120 

If 99 132 

1| 107 144 

If 115 156 

If 118 168 

1| 125 180 

2 126 192 

2^ 140 204 

3 141 216 

4 144 228 

Table H. 

Discharging Comparative Same by Cal- 

Distances in Inches. Quantities. culation. 

1 42 

2 56 84 

3 60 126 

4 66 168 

52. In these experiments the true ratio may be observed 
until the distance between the balls bears a certain relation to 
their distance from the external and denser atmosphere; after 
which, as appears by table G, the quantities of electricity re- 



Mr. Laming on the primary Forces of Electricity. 51 

quired by that ratio become less by certain decrements, in- 
creasing for some distance nearly in arithmetical progres- 
sion. 

53. That the comparative contiguity of the sides of the re- 
ceiver really produced the apparent discrepancies, was verified 
in two different manners ; first, by substituting for the balls 
between which the discharges were taken others of smaller 
size, by which the true ratio was extended to a greater di- 
stance; and secondly, by replacing the receiver by others, 
first of greater, and then of lesser dimensions, in which case 
the extension of the true ratio became also greater and less 
respectively. 

54«. It would appear from this that in the discharge of a Ley- 
den jar through long tubes of glass filled with rarified air, al- 
though the charge emanating from the ball connected with 
the positive coating really enters the ball proceeding from 
the negative coating, the free electricity is first attracted and 
passed onward, by induction, by the more contiguous bodies; 
and this view of the case not only explains the sensible passage 
of electricity along the surface of the glass, as frequently ob- 
served in experiments of this kind, but it makes clear also 
certain other phasnomena of a similar nature which otherwise 
would not be well understood. 

55. For example, a quantity of free electricity, which under 
ordinary circumstances may be discharged through the sub- 
stance of a conducting body, perhaps heating it to redness, 
or even fusing it, will if the experiment be made in rarified 
air pass only along its surface * ; a phaenomenon which we 
may refer to the inadequate resistance by the minor force 
in the conductor to the intensity of the major force acting 
in the opposite direction, and now made very great by reason 
of the reduced quantity of its contiguous compensating at- 
mosphere. 

56. Let us in the next place examine our principles with 
reference to the phsenomena which ensue when both the plus 
and the compensating conductors are in a state of insulation. 
Already it has been explained, that such bodies may compen- 
sate free electricity, by becoming themselves positively elec- 
trical (12.); and we have had abundant opportunity of con- 
templating such an induced electrical condition as we find it 
impressed on the insulating atmosphere in which experiments 
for the most part are conducted : we shall do well to consider 
also the same condition as it may be induced in insulated 
solids. 

* PhU. Trans. 1834, p. 242, and Singer's Elements of Electricity, p. 63. 

E2 



52 Mr. Laming on the primary Forces of Electricity, 

57. Imagine a plane surface A, to be insulated and charged 
with free electricity ; its compensator will be the contiguous 
atmosphere, this being an insulator acquiring in consequence 
a plus condition. Suppose now a second similar plane B, 
also insulated, to be placed parallel to A, and within its com- 
pensating atmosphere ; it will in part assume the compensa- 
tion of the plus charge, becoming in consequence itself" posi- 
tively electrical by the retention of its own equivalent of elec- 
tricity, and thus be in its turn compensated by a stratum of 
atmosphere, whose electrical condition also will for a similar 
cause be positive. 

58. Under these circumstances the intensity of electrical 
attraction in B as measured by an electrometer will be greater 
as its distance from A is less, and less at any particular distance 
as its atmospheric or other compensation is more perfect. 

59. But the compensation and the distance being given, the 
intensity induced in B will vary as the square of the quan- 
tities of free electricity in A directly (8.). 

60. Let P and N, fig. 2, be insulated conductors charged 
to an equal extent, the first positively and the other nega- 
tively; each being compensated by the surrounding portions 
of atmosphere n 7i' and^jj'. Let C, a cylindrical conductor, 

Fig. 2. 

f \ / \ 

, — ,n' \ / fi' — 



(O) 



lO) 



N 



be so interposed midway between P and N, that one of its 
ends shall by becoming negative assume part of the compen- 
sation of P ; and its other end by becoming positive assume 
a corresponding part of the compensation of N. Thus si- 
tuated, if the force of major attraction be great enough to 
overcome the minor attraction, all that portion of free elec- 
tricity in P which is not compensated by the inner spherical 
stratum of air w' (at a less distance) will pass into the near 
end of the conductor ; at the same time that the plus charge 
of its other end will pass into N, leaving the latter still nega- 
tive to the amount of its plus compensation by the inner stra- 
tum of air p^ In either of the electrified bodies a residuum 



Mr. Laming on the primary Forces of Electricity. 53 

of its former charge will then remain, until by their increased 
contiguity to the conductor C it is enabled again to assume 
the compensation. 

61. Again, let P N be charged as before, and the conductor 
C, now terminated by points^ be introduced as shown in the 
figure; the free electricity of its plus extremity p' will be re- 
tarded with less force than in the previous case, when its ends 
were blunt; and the minus common matter of its point w' 
will, in consequence of its reduced size, sustain the compen- 
sation of a much larger comparative quantity of free electricity 
in P, and accordingly exert a corresponding intensity of 
major force. 

62. Such an insulated conductor of given figure as Cou- 
lomb has called a proof plane applied successively to different 
parts of the surface of a plus conductor of irregular figure, 
will during each contact sustain an amount of atmospheric 
compensation proportionate to that of the part against 
which it is applied ; and hence become charged with a quan- 
tity of free electricity proportional to the quantity accumu- 
lated on that part. But on removal from the charged sur- 
face it will in all the cases acquire the same amount of atmo- 
spheric compensation ; and consequently in each case an in- 
tensity of charge varying as the square of its quantity of free 
electricity. 

63. The preceding deductions of the theory embrace all 
the most important cases of what is ordinarily called elec- 
trical action, that is to say, of the action of free electricity 
accumulated on the surface of conductors. Their experi- 
mental illustrations are too obvious to need, and in so short a 
paper too multitudinous to admit of, being specified. The 
accordance of theory and fact may not in all cases appear at 
first sight, especially if any of the steps in the argument 
brought forward have been treated in a cursory manner ; but 
if they be attentively considered in series, they will, I appre- 
hend, bear the strictest criticism. 

64. In concluding this part of the theory it becomes neces- 
sary to add an important observation or two. Without having 
entered into the question of the cause of Coulomb's law, we 
have hitherto confined ourselves to the facts embraced by it in 
order to show their perfect consistency with the doctrine of 
compensation, which we have shown to be a function of the 
major electrical force and necessarily proceeding from its de- 
finite nature. I cannot but believe that in doing this I have suc- 
ceeded in proving that the repulsive force supposed to be in- 
herent in electricity, or in electrified bodies, is superfluous ; and 
that all the phsenomena which are commonly ascribed to such 



54- Mr. C. Binks on Electricity, 

an influence admit of an easy solution on the sole principle of 
attraction. On this part of the subject there is, however, one 
seeming difficulty, which may have suggested itself, in as much 
as it may be thought to be an inevitable consequence of the 
minor electrical attraction that the electrical atoms be brought 
together by it into indissoluble union. In reply, I am pre- 
pared to show, that neither such an effect, nor any other 
which is inconsistent with facts, would follow, if we were en- 
tirely to expunge repulsion, as a principle of action, from our 
systems of physics. 

65. But what I have more particularly to state here is, that 
it will be seen in the pages which are immediately to follow, 
that although the law of Coulomb accurately expresses the 
sensible effects of the action of electricity on common matter 
in general, we have not on record a single instance of that 
action that may not be minutely and circumstantially traced 
to matter at insensible distances*. In the same place we shall 
be able to explain also the particular action by which the 
electrical state of one body may become compensated by the 
opposite electrical state induced in some other body at a 
sensible distance, and which was purposely passed over in an 
early article as being premature (7.). 

London, April 17, 1838. 

X. On some of the Phaenomena and Laws of Action of Voltaic 
Electricity, and on the Construction of Voltaic Batteries, 
Sfc. By Christopher Binks. A second Communication, 
addressed to J. F. Daniell, Esq. F.R.S., 8^c. Professor of 
Chemistry in Kin^s College, London. Part the First.^ 

Section I. — Subjects of Inquiry, 
My dear Sir, Edinburgh, April 9th, 1838. 

1. TT^HE paper which I now have the honour to submit 

to your attention is occupied with the details of an 
experimental inquiry into subjects which have had their origin 
as follows: 

2. You will remember that in my last paper $ I stated as 
the results of certain experiments that any voltaic arrange- 

* Since these pages have been in the hands of the printer, I have been 
favoured by a sight of the forthcoming [Eleventh] series of Dr. Faraday's 
admirable " Researches ;" in which that assiduous and successful philo- 
sopher labours to prove by experiment that electrical induction is trans- 
mitted to distant bodies by intervening matter. How well this experience 
accords with the new theory, will more fully appear in the ensuing part 
of this paper. 

f Communicated by Professor Daniell. 

X Lend, and Edinb. Phil. Mag., July 1837. 



Voltaic BatterieSf 8fc. 55 

ment, whether simple or compound, whose elements were 
zinc, copper, and dilute sulphuric acid, appeared to be placed 
in the best circumstances for the exercise of its full power 
when under either of these two conditions ; — first, when the 
extent of the copper surface was sixteen times greater than 
that of the zinc ; or, secondly, when the surface of the zinc was 
made the greater of the two in the proportion of about seven 
to one of copper. 

3. To state these results more definitely, let the zinc plate 
first used have an area, on each surface, of one square inch, 
and let its associated copper plate be of the same size. The 
voltaic action resulting from this arrangement being ascer- 
tained and taken as unity, and as a standard of comparison, let 
the zinc and all other conditions remain as at first, but let the 
copper plate be displaced by others, successively, whose areas 
increase in a regular progression ; when it will be found that 
with a copper plate of two square inches on each surface, or 
twice the size of the first, the action will be equal to 1*3; 
with one of four square inches, equal to \'Q\ and so on, by a 
certain progressive rate of increase till we reach to an area of 
16 square inches, when the action will be found to have ar- 
rived at its maximum, and to be, in numbers, equal to 4*6. 

4. Beyond this point the action will be augmented by no 
further addition whatever to the size of the copper plate ; but, 
on the contrary, such further additions cause as remarkable a 
progressive decrease. 

5. And, on the other hand, when we retain the copper 
plate of one square inch first used, but substitute for the small 
zinc one others of zinc in succession, progressively larger, a 
corresponding progressive increase of action will likewise fol- 
low till the zinc plate becomes of an area of about 7 square 
inches, at which point the greatest amount of voltaic action 
will be obtained, being in numbers equal to about 3 compared 
with the standard amount of 1 ; and this amount will suffer 
neither increase nor diminution by any subsequent addition 
whatever to the dimensions of the zinc plate. 

6. The relative proportions of the two plates at which the 
maximum effect took place as thus determined, were obtained 
when both surfaces of the zinc, as well as both surfaces of the 
copper plate, were exposed to the action of the exciting acid ; 
thus making, in the case in which the copper is the larger, a 
total area of 2 square inches of the zinc and 32 square inches 
of the copper, and constituting a ratio of 1 to 16. 

7. But subsequent experiment (see section 8th) has deter- 
mined that this same extent of copper surface is needed as 
well when only one, as when both surfaces of the zinc are 



B6 Mr. C. Binks on Electricity, 

engaged in the operation ; provided that if one surface only 
of zinc be so employed, it be that surface which is directly 
opposite to the copper. It has been determined that the con- 
trary surface of the zinc serves merely to increase the inten- 
sity of action, that is, the quantity in a given time, and in no 
respect to influence the required area of the copper plate, 
that being determined solely by the area of that surface of the 
zinc plate which is opposite to it. These phaenomena are 
more fully entered upon in a subsequent stage of the experi- 
ments in this paper; but it is proper to remark here, that the 
relative proportions of the two plates may be determined un- 
der either of the above conditions, either when both surfaces 
of the generating plate or when only one is employed ; esta- 
blishing in the former case a ratio of 1 to 16, and in the latter 
of 1 to 32; but as the latter is the ultimate condition of the 
experiment, it is that which, in a theoretical point of view, 
will be considered the more important. 

8. Besides some important theoretical considerations which 
attach to these results, they were immediately serviceable in 
reconciling the conflicting statements which had previously 
prevailed respecting the best relative proportions of the two 
metals; and in showing how, at the will of the inventor, any 
voltaic battery could be brought to exercise a maximum ef- 
fect, though different in degree, by having either the zinc or 
copper plates the larger of the two throughout the series ; and 
also (wherever the same elements are employed) in showing, 
numerically, the comparative amount of action which can be 
obtained under any conditions whatever of the proportions of 
the two metals, and of the strength of the exciting acid. 

9. The correctness of these former experiments, so far as 
they were then carried, is now abundantly confirmed by other 
experiments differently conducted ; and their results will be 
found ultimately to be deducible from a general law, which 
will be endeavoured to be established towards the conclusion 
of this paper. 

10. The particular laws formerly arrived at were obtained 
equally for compound as for single arrangements, and for 
acid solutions of every strength, or for every degree of activity 
of the generating agents. But they were sought for under 
one condition only as regarded the distance of the elementary 
plates from one another. It was then distinctly slated *, that 
to preserve uniformity in this respect, the plates were main- 
tained exactly one inch apart throughout the whole inquiry ; 
so that any modification of the results of experiments that 

* Page 71, Phil. Mag., July, 1837. 



Voltaic BatterieSi 8fC. S7 

might have occurred by having the mass of interposed fluid 
of variable dimensions was thus avoided. In only one instance 
was this deviated from, when the plates were removed from the 
distance of one inch to that of two inches, which alteration, 
as will presently appear, was too small materially to affect the 
results of the experiments as they were then conducted. 

11. My first object then is to examine these phaenomena 
(already determined for one such case) when in connexion 
with every possible condition as regards the distance of the 
elementary plates from one another ; or as they are modified 
by having the mass of interposed fluid of variable dimensions. 

12. Such an inquii'y necessarily includes a repetition of 
my former experiments, since it becomes requisite to find the 
area of that plate which at any given distance yields the max- 
imum effect, as well as to find the effects abstractedly of dif- 
ferences in the distance, and the influence of acid solutions 
of different degrees of strength. 

13. Until recently, the magnetic needle has usually been 
employed to detect and estimate comparative quantities of 
voltaic electricity evolved by ordinary arrangements. When 
the results brought out by the preceding inquiry had been 
satisfactorily ascertained, it was made apparent that between 
them and others previously determined and admitted as cor- 
rect, there existed a singular disagreement. It became de- 
sirable, therefore, to endeavour to reconcile the two methods 
of observation ; and with this view the experiments which oc- 
cupy the second part of this paper were undertaken ; having 
for their object to determine the relation between the deflec- 
tions of the magnetic needle and the quantity of zinc and 
other elements expended in producing those deflections; or, 
in other words (if the principle of observation here employed 
be correct), to determine the relation between the quantity of 
electricity and the deflections it produces. 

14. Chemistry has determined the kind of changes which 
occur among the elements here employed to evolve voltaic 
electricity; but we know not whether its development be due 
to the influence of one or more, or all these changes. We 
have first the resolution of the water into its constituent 
parts ; the appropriation of the oxygen by the zinc, and the 
appearance of the hydrogen, as gas, upon the copper; the 
formation of the oxide of zinc, and, subsequently, of the sul- 
phate, and the solution of that salt in the water. The present 
doctrines of chemistry require that these changes should fol- 
low consecutively, but, as far as we can perceive, they are si- 
multaneous. 

15. Let some of the attendant phaenomena be examined on 



5S Mr. C. Binks on Electricity, 

the hypothesis, that the development of the electricity, in the 
present case, is due to the occurrence of a physical change in 
the condition of the water itself; water is a compound of two 
measures of hydrogen and one of oxygen. The oxygen being 
distributed over the whole surface of the zinc, and there com- 
bining, it might be presumed that the hydrogen would appear 
on an extent of surface corresponding to its combining volume, 
or on a surface of twice the area of that occupied by the other. 
Or the presumption might be, that the surfaces required would 
correspond to the difference between the bulks of the metallic 
zinc expended, and of the liberated hydrogen; or between 
the bulks of the oxide of zinc produced and of the hydrogen ; 
which latter differences are immense, though not beyond the 
reach of experiment. 

16. But an appeal to experiment at once decides the ques- 
tion, and shows that the relation is none of those just pre- 
sumed, nor of any other that could have been determined by 
any a priori reasoning. It is found that the relation between 
the two surfaces upon which the constituents of the water re- 
spectively operate or appear, is as one to thirty-two ; or di- 
rectly as the volumes of one quantity by weight of oxygen, 
and two quantities by weight of hydrogen. 

1 7. So soon as this unexpected relation had been found by 
actual experiment, it became a matter of interest to inquire 
whether or not it were an instance of the operation of some 
general law hitherto unknown, or a mere accidental coinci- 
dence. It would have been premature to anticipate the na- 
ture of that law on the indications of one instance merely ; 
and it has consequently become the object of the experiments 
contained in the third part of this paper to examine into as 
many instances of voltaic action, in connection with the phy- 
sical and chemical characters of the products resulting from 
that action, as may be necessary to determine the nature and 
extent of that law thus suspected to exist. 

18. And respecting this part of the present inquiry I may 
be permitted to add, that whether it be considered with regard 
to its immediate object, or to the novelty and range of the ex- 
periments to which it necessarily leads, to the number of cu- 
rious relations it serves to detect, or to its bearing upon some 
others of the collateral sciences, particularly upon chemistry, 
I know of few others connected with electricity in which an 
experimentalist can feel a greater interest. 

19. The following experiments were begun in the pursuit 
of these three general objects ; but it is almost needless to re- 
mark that others have arisen as the inquiry has proceeded, 
but which will best appear in the order of their occurrence. 



Voltaic BatterieSi 8fc, 69 

The arrangement of the experiments which is here adopted is 
very nearly the same in the order of succession as that in 
which they were made, and differs from that order only so far 
as has appeared desirable, in order the more clearly to show 
the results actually arrived at, and at the same time to indi- 
cate progressively the evidence for other results anticipated, 
but the completion of which can be reached only at a more 
advanced stage, or at the conclusion of the whole inquiry. 
You will permit me also to refer to the circumstance, that 
occasionally throughout the statements which follow I have 
thought it desirable to make explicit and repeated references 
to many minute and well-known details involved in researches 
of this nature, which in writing to one with whom the subject 
is so familiar, and to whom each particular would be sug- 
gested by the matter in immediate connexion, may appear to 
be somewhat unnecessary^ But as I am aware that my paper 
may not be confined to your own perusal, I have preferred to 
aid any demonstrations it may attempt by a recurrence to 
such details, made explicitly and wherever they might appear 
useful, rather than, for the sake of inserting only that which 
is perfectly novel, to omit them, and thus lose the advan- 
tage of as much clearness in description as the nature of 
the subject itself might otherwise admit of. 

Section II. — The Principle of Investigation. 

20. The principle employed throughout the following in- 
vestigation to detect and estimate effects, has arisen out of 
the discovery of Faraday of the definite character of voltaic 
action. 

21. The experiments which served chiefly, in the hands of 
its discoverer, to establish this great principle, were those in 
which a current of electricity, evolved by a compound arrange- 
ment, was passed through water, when it was found, first, that 
the water which such a current decomposed, bore, in its quan- 
tity, a definite relation to the quantity of the elements by whose 
mutual action that current was produced ; and, secondly, that 
the quantity of any other body than water, which the same 
current decomposed, was likewise definite, and bore a fixed 
relation both to the quantity of water first decomposed and 
to the quantity of elements expended in any one cell of the 
generating battery itself. And the relations thus presented 
were found to be exactly the same as the relations between 
the different respective chemical equivalent numbers of the 
bodies engaged in the operations. So that, for example, in 
the instances of the zinc expended in any one cell of the bat- 



60 Mr. C. Binks on Electricity, 

tery, and of the water or of the muriatic acid which such bat- 
tery decomposed, the quantities were, for the first, 32, for the 
second, 9, and for the last 37, or exactly as their equivalent 
numbers. 

22. The distinguished author of this discovery subsequently 
extended this principle into an inquiry as to the origin and 
nature of this voltaic action — into an estimate of the absolute 
quantity of electricity associated with the particles of matter, 
and also into an estimate of the comparative quantities of 
electricity evolved by different agencies, &c.; but the general 
results which I have more particularly in view at this moment 
are those from which it was deduced that chemical and elec- 
trical action, if not identical, are co-existent, and equal in 
quantity and effect. 

23. The application which I make of this principle to the 
present investigation is exceedingly simple and obvious in its 
nature : the elements engaged in the phaenomena now exa- 
mined are, water, sulphuric acid, zinc, and copper. Since the 
last I'emains unchanged, or subserves its purpose best when 
unchanged, it may be considered as a mere instrument en- 
gaged in aiding the chemical and physical changes which take 
place among the others, through whose mutual action the 
electricity itself seems to be evolved. To ascertain the quan- 
tity of electricity so evolved, it is only necessary to ascertain 
(on the principle just stated) the quantity of matter employed 
in its production ; and this can be done by finding the quan- 
tity of zinc expended or of sulphuric acid, or of water decom- 
posed, or the quantity of hydrogen evolved, or of sulphate of 
zinc finally produced. But as chemistry has already deter- 
mined the relations of these substances one to another, it is 
only necessary to find the quantity of any one of them, to know 
the quantity of every other. In the present instance it is most 
expedient to find the quantity of the zinc so expended by 
weighing the zinc plate both before and after the operation, 
or to measure the quantity of the evolved hydrogen ; or, if it 
be the effect of the power of a compound battery which is to 
be found, then, to measure the quantity of both the gases 
produced by its action, a contrivance adapted to the last pur- 
pose constituting one of the forms of the voltameter of 
Faraday. 

24. The phaenomena examined into in the first part of the 
present paper, are those resulting solely from the action of 
single voltaic arrangements. Let such an elementary arrange- 
ment, having its plates of a certain size, and placed at a cer- 
tain relative distance, be acted on by an acid mixture of a 
certain degree of strength. The amount of action which will 



Voltaic Batteries^ S^c. 61 

take place in such an arrangement, under such circumstances, 
will be altered if the plates be made larger or smaller, or if 
the strength of the acid or the distance of the plates from one 
another be altered. But the action resulting from any of 
these three modifying causes is still of the same kind though 
different in degree ; and it is with the finding of the amount 
of these differences in degree, in connexion with the circum- 
stances which cause them, that the first part of this paper is 
chiefly occupied. 

25. These degrees of action may either be considered as 
degrees of chemical or of electrical action. The operations 
themselves are chemical ; and the quantity of chemical action 
is determined by the quantity of matter which has been em- 
ployed in it. But this chemical action is induced by a voltaic 
arrangement ; and on the principle stated above, that if not 
identical, these two kinds of action are co-existent and equal 
in quantity and effect, the quantities now determined by ex- 
periment may be considered as quantities either of chemical 
or of voltaic action: by whichsoever name they may bef called, 
the experimental results themselves remain unaffected. 

26. These explanations are called for to show the connex- 
ion which the method I here employ has with the principle 
discovered by Faraday ; and to show also in what respects 
its results may be wholly dis-associated from any of the mere 
theoretical considerations which have followed that discovery. 
The details which follow are confined solely to the progress 
and results of experiment ; or to such general conclusions 
only as seem to be warranted by a sufficiency of incontestable 
evidence. 

27. The preceding remarks apply equally to the method 
used in the 2nd and 3rd parts of the following paper, though 
the ultimate object in each is different. 

28. The particular objects of the 1st and 2nd parts have 
perhaps been already sufficiently adverted to, but this seems 
to be the proper place, immediately after the preceding re- 
marks, to define the precise object more particularly aimed 
at in the third. 

29. The researches of Faraday have proved that in one 
great class of its phenomena the action of electricity is defi- 
nite; and in another class (more particularly examined in 
the 3rd part of this paper), but entirely different from any ex- 
amined by Faraday, it will subsequently be shown that the 
same principle prevails. In the former case the phaenomena 
so examined related chiefly to the influence of quantity of 
electricity both as regarded its production and its effects. In 
the latter case the examinations do not regard the production 



62 Mr. C. Binks on Electricity, 

or effects of electricity abstractedly, but relate chiefly to some 
of the physical conditions under which its operations take 
place, and more particularly to the relative spaces occupied 
by the agents engaged in its operations. The law deduced 
by Faraday was, that the influence of electricity over bodies 
subjected to its action was directly as its quantity, and as the 
equivalent numbers of the bodies themselves. The results 
which will be attempted here to be established (but of which 
one instance only has as yet been adduced, in paragraph 16) 
are, first, that the superficial areas of the spaces within which 
this electrical action takes place, have a definite relation to 
the kind of bodies occupied with that action ; or, more speci- 
fically, that the superficial areas of the electrodes have a de- 
finite relation to the kinds of bodies which, by the force of 
voltaic action, are determined to those electrodes ; and second, 
that the law which expresses these relations is, that the rela- 
tion between the areas of the two electrodes is inversely as the 
relation between the specific gravities of the bodies respectively 
determined to those electrodes, each area being multiplied by 
the comparative number of volumes of the body determined 
to it. 

30. So that in the instance already referred to (16), where- 
in the bodies so determined are hydrogen and oxygen gases, 
we have their relative specific gravities as 1 and 1 6 ; but these 
bodies have resulted from the binary compound water, in 
which their volumes are not equal, but as two to one. So 
that when the numbers expressing the specific gravities are 
used inversely to represent the areas of the two electrodes, we 
have those areas as 1 6 and 1 ; that is, the area of that electrode 
at which the hydrogen appears being inversely as the sp. gr. 
of the hydrogen, is equal to 1 6, and that of the oxygen equal 
to 1 ; which numbers, being multiplied respectively by the 
number of volumes in which these two bodies occur in this 
case, give 16 (area) x 2 (vol.) = 32 for the area of the hydro- 
gen electrode; and 1 (area) x 1 (vol.) = 1 for that of the 
oxygen ; which proportions are exactly those of the copper 
and zinc plates as found by actual experiment, the surface of the 
copper plates yielding the maximum effect in any such arrange- 
ment requiring to be 32 times greater than that of the zinc. 

31. Or, in another view, the expression of the same law 
may be, that the relative areas of the two electrodes are di- 
rectly as the relative bulks of equal weights, multiplied by the 
number of volumes of the two bodies respectively determined 
to those electrodes : so that in the same instance as above, in 
which the elements determined to each electrode are hydrogen 
and oxygen gases, we have the comparative bulks of equal 



Voltaic Batteries, Sfc. 63 

weights of each as 1 6 to 1 ; but there are two volumes of hy- 
drogen and one of oxygen, so that the bulk of the equal weight 
of hydrogen, being multiplied by its number of combining 
volumes, gives 16 x 2 = 32, and the oxygen gives 1 x 1 =1, 
which is precisely the relation between the areas of the two 
electrodes which is found to obtain when the question is sub- 
mitted to experiment. 

32. And it also follows, that if these relations have been 
determined for the superficies of any such arrangement, they 
have been determined likewise for every other geometrical re- 
lation peculiar to it ; and again, that if they have been ascer- 
tained for the electrodes, and the bodies determined to the 
electrodes, they have also been determined for the compound 
from which these bodies have been derived, or, in other words, 
for the electrolyte — so that the expressions of the law just 
stated may be varied so as to include any or all of these re- 
lations. 

33. The expressions of this law as just stated are framed in 
accordance with the present theoretical notions of equivalent 
numbers, volumes, &c., but it is easy to foresee how investi- 
gations of the kind now spoken of, when they shall come to 
be conducted with sufficient nicety, may be used either to con- 
firm or modify the theories at present entertained on some 
of those points. 

34-. This general law will not include all the phaenomena 
attendant upon the operations now referred to ; but a series 
of subordinate laws will be needed to express what have already 
been distinguished as primary and secondary effects : — but not 
further to anticipate these results, the preceding remarks will 
perhaps sufficiently indicate the precise nature of the subject 
with which the third part of this paper is intended to be 
occupied. 

35. It appears, therefore, that the definite character of vol- 
taic action may be proved to extend into other classes of its 
phaenomena, besides that in which its discoverer first detected 
it; and it seems unquestionable that the same principle prevails 
throughout all its operations, and that in the end every class 
of its phaenomena will be found to be governed by a law pecu- 
liar to itself. The general law of Faraday, and that just 
stated, are in perfect harmony with the previously well-known 
physical and chemical properties of the bodies engaged in the 
phsenomena from which they have been deduced ; and these 
two laws themselves will undoubtedly be found in the end 
equally to harmonize with each other. It seems not to be an 
unwarranted probability that if the laws peculiar to every such 
class of voltaic action were accurately determined, we should 



6-fr Mr. C. Binks on Electricity^ 

then have furnished to us a collection of data move valuable 
in themselves, and better calculated perhaps than any yet ob- 
tained to enable us to approach to the discovery, if not actually 
to reveal the real nature of this peculiar but still mysterious 
agent. 

Section III. — The Method of Investigation and preliminary 
Experiments. 
36. After some preliminary trials the following method was 
selected for conducting these experiments. A wooden trough, 
made water-tight by cement, and measuring 50 inches long, 
7 wide, and 7 deep, had its upper horizontal edge marked off 
from one end to the other into divisions of inches and fourths 
of inches. At the end from which this graduation began, wag 
fixed the zinc-plate to be experimented with, and the first di_ 
vision, marked 1, was exactly one inch from the surface of the 
plate itself, and the plate was about one inch from the extreme 
end of the trough, which consequently was divided, beginning 
from the zinc-plate, into 48 inches and fourths of inches, or 
in all into 192 parts. At the zinc end was fixed the cup, hold- 
ing mercury, in which the connexion between the two experi- 
mental plates was to be completed. The zinc plate was con- 
nected with a short wire, always of the same kind and length, 
and each copper plate was soldered to a wire 5 feet in length ; 
so that at whatever position the copper plate might be placed 
within the trough, whether at the distance of \\h of an inch 
from the zinc, or at 48 inches, or at any position intermediate, 
the wire completing the circuit was always of the same length; 
these experimental plates were retained at any required posi- 
tion simply by bending their connecting wires twice or thrice 
at right angles and thus fixing them over the sides of the 
trough. It being intended to weigh the zinc-plate before and 
after each experiment, or to collect the gas evolved from the 
copper plate during the experiment, the former had its con- 
necting wire so short as not to interfere with its being readily 
weighed and replaced ; and the gas from the latter was col- 
lected in a funnel-shaped meter having its open base so large 
as to gather the whole of the gas sent off from the copper plate 
of whatever size that might be. The long tubular part of 
this meter was divided into tenths and fiftieths of a cubic 
inch, and its entire capacity was about 1^ of a cubic inch. 
The simple contrivance of a couple of strong glass rods, bent 
twice at right angles, supported by the sides of the trough 
and stretching across it, served as supporters for the meter, 
moveable at pleasure, and by which it could be suspended at 
any required position above the copper plate. The meter was 



Voltaic BatterieSi 8fc, 65 

readily refilled with liquid by immersion in the trough itself. 
Another trough and meter of larger dimensions were also pro- 
vided for such experiments as required the use of larger plates 
than such as could be introduced into the smaller trough. 

37. The zinc used throughout the experiments was always 
of the same kind and always amalgamated. Its equivalent 
number was 34*5, requiring in consequence of impurities con- 
tained in it 34*5 grains, instead of 32, to yield 1 grain of hy- 
drogen. The connecting wires both of the zinc and copper 
plates were partly covered, but to the same extent in each, 
with bee's wax, so as to protect them from the action of the 
acid, so far as they were at any time immersed in it, and to 
confine the voltaic action entirely to the surfaces of the plates 
which were the subject of experiment. The circumstance 
that the surfaces of the wires, protected by the wax, were of 
uniform extent in every case, will need afterwards to be re- 
membered. 

38. These precautions against error, by preserving uniform- 
ity in the kind of metal used, in the kind and lengths of the 
connecting wires, and in the extent of surfaces to be acted 
upon, are independent of other precautions requiring equally 
to be observed. A variety of modifying causes are incessantly 
operating in experiments of this nature, and producing effects 
of a most perplexing kind, each of which needs to be fully 
appreciated and guarded against, or as fully as possible cor- 
rected, in order to ensure any satisfactory degree of accuracy 
in the results of experiment. 

39. I. It has been shown by yourself*, that immediately 
afteV the first immersion of a zinc plate under voltaic arrange- 
ment, its amount of action is greatly impeded by an accumu- 
lation upon its surface of minute air-bubbles, which adhering 
to it interpose a surface of air between the plate and the ex- 
isting acid ; thus preventing the full voltaic action so long as 
they continue to be attached to the plate. By my own ex- 
periments I found that a zinc plate, after such accumulation 
had taken place, yielded a certain measure of gas in 240 se- 
conds, but by repeatedly clearing its surface from these bub- 
bles, by agitating it or otherwise, the same measure of gas was 
produced in two-thirds the time, or in 160 seconds. When, 
however, the copper plate is at its maximum size in any ar- 
rangement little or no such accumulation occurs. 

40. II. The gas arising from the copper plate will do so 
more rapidly if the water be agitated than if it remain tran- 
quil during the action : an arrangement yielded voltaic action 

* Phil. Trans. 1836. 
^ Phil. Mag, S. 3. Vol. 13. No. 79. July 1838. F 



66 Mr. C. Binks on Eleclricity, 

equal to one measure of gas in 80 seconds, during the agita- 
tion of the water occasioned by refilling the meter ; but after 
it had become again tranquil the same measure was produced 
in 95 seconds, or in a length of time greater by about one- 
fifth. It is almost needless to remark that this increased 
action is due solely to the mechanical effect of the water when 
in motion displacing the air-bubbles as rapidly as formed, and 
more rapidly than they would otherwise be displaced by rea- 
son merely of their superior levity. 

41. III. Another mechanical effect of a similar kind, but 
operating to a much greater extent than in either of the pre- 
ceding instances, is induced by the mere position of the plate 
from which the gas is evolved : if the surface of a copper 
plate be placed in a horizontal plane, the gas which is gene- 
rated on its under side will remain continually attached to the 
plate ; and should that be the only surface operating, the vol- 
taic action of such an arrangement would be almost com- 
pletely impeded; but, on the contrary, if it be placed and 
used in a vertical plane, then the only causes likely to obstruct 
the ready dismissal of the gas from the surface are the com- 
paratively minute ones just referred to in II. 

42. IV. A copper wire which had been stretched in order 
to straighten it, previously to its being attached to a plate, 
was found to give a voltaic effect about one-fifth less than 
another, in all other respects the similar, but which had not 
been so extended ; but the conducting power of the former 
was again restored by exposing it to heat. And, again, two 
wires, in all other respects alike, but which had accidentally 
been heated in different degrees, gave a marked difference in 
amount of action ; but had their uniformity of conducting 
power restored upon exposure to an equal temperature. 

43. V. The same remarks apply equally to plates as to 
wires ; but there is another cause of variation in the action of 
plates not previously recognised. In an extensive course of 
experiments connected with the subject of this paper, in which 
I had completed about 15 tables of results, each table con- 
taining, on an average, about 10 observations, I was sur- 
prised, on looking these tables over, to observe that there was 
presented invariably (under whatever conditions the experi- 
ments might have been performed) a remarkably increased 
amount of action opposite to a number representing one par- 
ticular copper plate. Since no probable cause could be as- 
signed for this recurrence, except that of some property pecu- 
liar to the plate itself, another plate was substituted for it, 
when it was found that throughout the whole inquiry the 
plate in question had been giving nearly double its amount of 



Voltaic Batteries^ Sfc. 67 

action. It was now remembered that this particular plate 
had been cut from a piece of copper which had been employed 
in some former experiments, during which it had been partly 
amalgamated, and had had one of its sides covered with bee's 
wax, to remove which and the mercury previously to adopting it 
to its present use, it had been thrown on the surface of a bright 
fire, and afterwards, whilst nearly red hot, had been plunged 
in a trough containing dilute sulphuric acid. The same plate 
was the agent in another curious phaenomenon, to be men- 
tioned subsequently. (See Section VIII.) But confining my- 
self to my present purpose, and without further alluding to 
this circumstance, or to the suggestion it affords of a means 
of increasing the power of voltaic arrangements, by some such 
treatment of the plates, it is necessary here to remark that so 
soon as this condition of the plate was detected, both the whole 
of the plates, and the results of the experiments in which they 
had been engaged, were dismissed as uncertain, and the whole 
repeated with the use of new plates prepared with every pos- 
sible regard to uniformity in their condition in every par- 
ticular. 

44. VI. The copper plate of any voltaic arrangement very 
speedily has its surface so affected as to be greatly diminished 
in its amount of action ; an effect arising in some case from a 
partial action upon the copper itself, but caused more fre- 
quently by a deposition of matter upon its surface, derived 
from the solution it is acting in ; and consequently differing 
in kind and degree according to the nature of that solution, 
and to the intensity of the voltaic action itself. If a copper 
plate be so used through a period of 30 minutes, and its 
amount of action be examined during every five minutes of 
that time, it will be found that this diminishing in effect will 
proceed much more rapidly during the latter than the former 
portions of that time, as is shown in the following table : 

No. 1. 

Periodsoftimeof 5 minutes') , . „ i „ -, .^i ^,, ^,, 
ggjjjj^ > 1st. 2nd. 3rd. 4th. 5th. 6th. 

Measures of gas in 50ths of ^ 

a cubic inch yielded in > 35. 33. 29. 24. 17. 9. 
each time. J 

And when at the end of these periods the surface of the cop- 
per was again brightened, its action was restored to the first 
amount, or to 33 measures in the same time. 

45. This table is not unimportant, inasmuch as it might 
have occurred that the accelerated action which takes place 

F2 



68 Mr. C. Binks on Electricity^ 

by continued immersion upon the zinc plate might be com- 
pensated for by the retarded action occurring upon its asso- 
ciated copper plate. But the rates at which the one is acce- 
lerated and the other diminished are different, as this table 
serves to show, and consecjuently any method of correcting 
such irregularities of action founded upon these opposite 
properties of the two plates would be futile. 

46. VII. The kind of polish also of the copper plate, and 
the cleanliness of its surface, have likewise a material influence 
upon its action, and consequently upon the results of experi- 
ments conducted with any measure of accuracy. The plate 
becomes soiled by frequent handling, and particles of the wax 
from the adjacent wires are liable to be transferred to its sur- 
face, and in the end, by their accumulation, almost .totally to 
obstruct its further action. 

47. VIII. Again, the action of any voltaic arrangement is 
greatly affected by the condition of the surface of the zinc 
plate, as regards its roughness or smoothness. An irregular 
rough surface of zinc will give a greater amount of action in 
a given time than one which has a fine polish. 

48. IX. And, on the other hand, an exceedingly irregular 
or rough surface of zinc, over which a profusion of mercury 
has been spread, will exhibit a less amount of action than 
another surface which is perfectly smooth, and over which 
only so much mercury has adhered as has been required to 
produce a perfect amalgam. These apparently contrary 
effects under like circumstances are easily explained : — the 
plate of zinc which is rough and full of cavities, on being suf- 
fused with mercury, presents but here and there a point of 
zinc amalgam to the action of the acid, the other parts of its 
surface being pure mercury ; whereas, in the other case, in ' 
which the surface is smoother and its cavities consequently of 
less extent, a greater number of amalgamated zinc points are 
exposed to the action of the acid, and the effect of the plate 
is consequently greater in proportion to the evenness of its 
surface. 

49. These different conditions of the zinc surface, however, 
are very different in their effects if the zinc be not amalga- 
mated; for in that case an entirely different principle of action 
is introduced ; but as it is amalgamated zinc alone which is 
used in these experiments, this particular need not be further 
alluded to. 

50. X. The insoluble impurities contained in common zinc 
accumulate upon the surface of a plate which has been long 
used, and unless removed from time to time will also serve in 
the end, and in addition to those causes already mentioned, 



Voltaic Batteries f S^c. 69 

to influence the action of such an arrangement. The conse- 
quences of this accumulation become strikingly obvious after 
a plate has been for some hours in use, and without having 
had its surface cleansed in the interval. 

51. XI. The particular position of the zinc plate whilst in 
action is needed as equally to be attended to as the position of 
the copper-plate {II1.)j though the necessity for this has a very 
different origin in the two cases. A zinc plate whose surfaces 
are placed in an horizontal plane will have the dissolved sul- 
phate of zinc resting upon its upper side, and hence inter- 
posing a stratum of comparatively inactive matter in the place 
of the existing acid. But when the plate is used in a vertical 
position, the dissolved sulphate continually subsides, by its 
superior gravity, from the surface of the plate; thus occa- 
sioning a perpetually renewed contact to take place between it 
and the fresh exciting acid. This effect may be rendered vi- 
sible when a glass vessel, holding an arrangement so suspended, 
is interposed between the eye and a strong light, when the 
varying refractions caused by the commingling of the two 
fluids of different densities, viz. the dissolved sulphate and the 
acid mixture, will show that a stream of the dissolved salt falls 
continuously from the bottom edge of the plate, and is finally 
diffused through the mass of surrounding liquid. 

52. XII. But the continually accelerating action occurring 
upon the zinc during immersion is the cause of a more fre- 
quent and variable kind of interference in these experiments 
than almost any other. A zinc plate whose surface is per- 
fectly smooth and truly amalgamated (such as are invariably 
employed in the subsequent experiments), will give a greater 
amount of action during a second time of immersion than 
during the first, as appears by the following table : 

No. 2. 

Equal times of immersionlj^^^ 2nd. 3rd. 4th. 5th. 6th. 

or 10 mmutes each . .j 
Measures of gas in oOths^ 

of a cubic inch yielded V 34-. 36. 38. 42. 50. 59. 

in each time ... .J 

"Whatever may be the strength of the acid used, or, in other 
words, whatever may be the total length of time needed to 
produce the same measure of gas, yet, when the plate has been 
affected to the same extent, whether that may have taken place 
in a longer or a shorter time, the difference between the rates 
of action in the first and last portions of the total time will 
be the same as exhibited by this table. 

53. XIII. Again, the acid solution becomes weakened by 



70 Mr. C. Binks on Electricity, 

continued use, and deteriorated by the sulphate of zinc dis- 
solved in it ; so that the results of any set of comparative ex- 
periments will be untrue, unless this source of variation and 
error shall have been completely avoided by the constant re- 
newal of the acid, or completely provided against by some 
system of correction adapted to its varied effects. 

54-. XIV. A voltaic arrangement, at the commencement of 
a set of experiments, when the apartment in which they were 
conducted was comparatively of a low temperature, viz. at 
53° Fahr., gave j^^^ of a cubic inch of hydrogen in 45 se- 
conds. But on the room becoming warmer, by means of the 
fire and lights used in it, the action of the arrangement was 
as progressively increased, and when arrived at the tempera- 
ture of 60° the same measure of gas was produced in 30 se- 
conds. Attempts were made to alter this activity of the ar- 
rangement by altering the surface of the zinc, by re-amalga- 
mating it and immersing the plates in cold water, but without 
effect; and the original amount of action was restored only 
after a free admission into the room of a current of a colder 
atmosphere, during a few hours, had reduced it to the original 
temperature. It is worthy of remark here, that whilst the 
atmosphere in the apartment suffered a change equal to 7 de- 
grees of temperature, the liquid the plates were acting in did 
not alter by more than two degrees ; and I have since had 
occasion constantly to observe that the changes in question, 
induced by temperature, in the activity of the arrangements, 
may be brought about equally when the surrounding atmo- 
sphere alone (that is, independently of any alteration in the 
temperature of the plates or the liquid) is the body which has 
undergone any perceptible change. 

B5. These effects of the influence of atmospheric tempera- 
ture, though ascertained by a different method and independ- 
ently, are in exact accordance, in general character, with 
those detailed by yourself, and respecting which you remark 
that " it is now, however, apparent that in the exact measures 
of different effects which an invariable current of electricity 
will enable experimentalists to undertake, the variations of 
atmospheric temperature even must not be neglected*." 

56. XV. There is yet another influence affecting the action 
of voltaic arrangements which has not, that I am aware of, 
been previously recognised; namely, the mechanical effects 
of the pressure of the column of liquid resting upon the plates. 
If in a trough, holding dilute acid and about 12 inches deep, 
a small zinc plate be fixed at half its depth or at 6 inches, 
and the associated copper plate of the same size be fixed, first 

* Philosophical Transactions, 1837. 



^ 1. 2. 4. 6. 8. 10. 12. 



>132'' 1S5" 142'^ 143'^ 147^' 154" 159'^ 



Voltaic Batteries, 8fc. 71 

at the depth of one inch from the surface of the liquid, and 
afterwards at the bottom or at the depth of 12 inches, but 
still at the same lateral distance from the zinc, the quantity of 
voltaic action obtained at each of these positions will be found 
widely different, as will be seen by the following table, in 
which the copper plate is moved through the same vertical 
plane to the different depths successively : 

• No. 3. 
Depth in inches of~ 
the copper plate 
from the surface 
of the liquid 

Time, in seconds,' 
needed at each 
depth to yield 
an equal mea- 
sure of hydro- 
gen ... ._ 

57. When the plate is near the surface of the liquid the 
hydrogen arises from it in a regular stream of exceedingly 
minute bubbles ; but when at a greater depth they are dis- 
missed from the plate irregularly and of a much greater size, 
having apparently adhered to it longer and with greater te- 
nacity than when nearer the surface. It is easy to conceive 
that previously to the dismissal of these larger bubbles from 
the surface of the plate, they will have prevented the direct 
contact of the acid and the copper by an interposed stratum 
of air, proportionate to the size of their bases, and hence have 
impeded the voltaic action itself. That these differences are 
due solely to the influence of pressure, in the present case, 
will be more distinctly shown subsequently (section 7th), when 
the precise relative positions of the two plates in these trials 
will need to be remembered. 

58. We perceive in the foregoing enumeration a variety of 
minute influences and effects, incessantly obtruding themselves 
into examinations of the nature of this present inquiry ; all of 
which, with the utmost care, need to be provided against, or 
as far as possible to be corrected, to ensure any degree of ac- 
curacy in the results of experiments. 

59. For the sake of a compendious reference to the methods 
by which these sources of error are obviated, or their effects 
otherwise guarded against throughout this inquiry, they may 
be classified as follows : 

60. 1st. Circumstances merely mechanical, affecting the 



7S Mr. C. Binks on Electricity, 

action of any arrangement, as position of the plates, agitation 
of the liquid, adherence of the gas to the plates, pressure of 
the column of liquid, &c., including the particulars stated in 
Nos. I., II,, III., XI. and XV, of the above enumeration. 

2nd. Circumstances of a mixed chemical and mechanical 
kind, affecting the surfaces of the copper plate, as its polish, 
cleanliness, &c., and stated in Nos. VI. and VII. 

3rd. Circumstances of the same kind, affecting the surface 
of the zinc, and included in Nos. VIII. IX. and X. 

4th. The temper, or conducting power of the wires and 
plates, as explained in Nos. IV. and V. 

5th. The influence of the general temperature under which 
the experiments are performed, as in No. XIV. 

6th. The effects of the weakening and deterioration of the 
acid mixture in No. XIII. 

7th. The accelerated action occurring upon the zinc in 
No. Xtl. 

61. To provide against each and all of these interferences, 
I adopt the following plans throughout the whole inquiry, 
and which being once distinctly pointed out, need not again 
be referred to in the course of the subsequent details upon 
other points, 

62. The zinc plate is removed from the trough at the end 
of each single experiment, and its surface cleansed by a linen 
cloth. The copper plate is polished with fine glass paper 
after each single experiment, washed with a solution of caustic 
potash, and then well rinsed in acidulated water before its re- 
turn for the next experiment. The observations of the mea- 
sure of gas generated in any given time, is not taken till the 
water has again become tranquil after the motion occasioned 
by replacing the plates and refilling the meter ; nor till after 
the complete suspension of the local action which generally 
takes place upon the first immersion of the zinc. (See 39.) 

The operating plates (unless where it is distinctly stated to 
the contrary,) have their central points always in one straight 
line, passing horizontally through the centre of the mass of 
liquid they are acting in, that in each set of comparative ex- 
periments the pressure upon the plates may be maintained 
uniform, and the plates themselves be preserved in a vertical 
position. The plates of either kind, which are here employed, 
are cut from the same sheet of metal, the wires from the same 
coil ; and the whole, after being adjusted, are exposed for some 
time to a like temperature, so that the temper and conducting 
power, as far as that depends upon the texture of the metal, 
may be the same in each. The temperature of the liquid and 
of the apartment in which the experiments are conducted is 



Voltaic Batteries^ Sfc. 73 

maintained as nearly as possible the same during the per- 
formance of any one set of experiments. 

63. These regulations sufficiently provide against every 
contingency that can affect the correctness of the experiments, 
except those of the gradually diminishing activity of the acid 
mixture through continued use, and the accelerated action 
upon the zinc which occurs during its continued immersion. 

64. Against the effects of these last, especial provision is 
made as follows : I prepare ten or a dozen of the kind of zinc 
plates which are the subject of present experiment, and bring 
each of those by previous management to yield the same 
amount of action in a given time. This is accomplished by 
taking one of them as a standard, and by polishing or roughen- 
m(r as may be needed the surfaces of the others, thus bringing 
each into precisely the same condition ; and a little practice 
makes this to be done with considerable facility. 

65. After any one of such a set has been used twice or thrice, 
its place is supplied with a fresh plate ; and after the whole 
number may have been so employed, the set is repolished and 
re-adjusted before their application to any new set of experi- 
ments. The extreme nicety which this plan introduces into 
experiments of this kind will be obvious if it be considered 
that each plate is employed to produce but at most five-tenths 
of a cubic inch of hydrogen before it is renewed, and conse- 
auently will have expended in that effort but little more than 
three-tenths of a grain of its entire weight; a quantity much 
too small to affect the action of the plate in any way likely 
to interfere with that degree of nicety which these experi- 
ments require. And with respect to the effect which so small 
a quantity of zinc will have upon the acid mixture, either by 
abstracting its active acid, or by impregnating it with the dis- 
solved sulphate, if it be considered that the quantity of acid 
mixture here employed is seldom less than eight or ten gal- 
lons, and that this too is frequently renewed, it will be obvious 
that the dissolving in it of even many such minute quantities 
of zinc will have no effect whatever upon the results of expe- 
riment. 

66. It will subsequently be seerrhow essential it is that each 
and all of the above particulars should be strictly attended 
to ; and preparations being thus made and observed through- 
out, I know of no other circumstances that can affect the ex- 
periments or interfere with their accurate performance; and 
the whole thus arranged admit of being performed with con- 
siderable ease and expedition. 

67. It has been thought better to place all these particulars 
under one view, at an early stage of this paper, as well to 



74 Mr. C. Binks on Electricity ^ S^c, 

show the precautions which have been observed to ensure ac- 
curacy, as to avoid the necessity for a continual reference to 
such details afterwards. 

68. The effects now to be sought for, are estimated gene- 
rally by the length of time needed to produce a certain mea- 
sure of gas, or for the expenditure of a certain weight of zinc. 
But it has been shown in some former experiments that the 
quantities of zinc expended and of hydrogen produced by it, 
(under certain conditions of voltaic action,) are not always 
equivalents of one another. In my former paper* a case of 
this kind is noticed, in which a small battery when used to de- 
compose water, lost zinc, in quantity one third greater than 
the equivalent of the hydrogen evolved. In the investigation 
that now follows no uncertainty will be permitted to remain 
upon this point; and the labour occasioned by such exami- 
nations will be found to have been not altogether without use. 
(See section 9th.) The measure of gas most commonly used 
is one tenth of a cubic inch, and the time is taken in seconds. 
With small plates, this measure will be yielded in a length of 
time ranging between 30" and 900" according to the strength 
of the acid or the distance of the plates. The moment at 
which this measure is completed by the meter, may be deter- 
mined with certainty within two or three seconds of the real 
time. A closer approximation than this is seldom attempted 
in the following experiments, nor is it in any respect neces- 
sary. The difference between 30 seconds and 900 seconds is 
an extreme one, and but seldom occurs : most commonly the 
difference is much less marked, and in some instances is so 
minute, that no other method, that I am aware of, than that 
now proposed is adequate to its detection. 

69. The capability of this method to detect minute differ- 
ences in quantity will be apparent upon a little consideration 
from what has been already said ; but the following compai'i- 
son between it and that afforded by an ordinary magnetic 
galvanometer, will serve to mark that capability more clearly. 

70. The galvanometer here used, though of the common 
construction, was an exceedingly good one, by Newman ; 
and such an instrument in all respects as would have been 
employed in the kind of experiments now made had the indi- 
cations afibrded by the needle been desired. 

71. The instance selected is an average one of the effects 
to be estimated. A small arrangement was used at first with 
its plates one fourth of an inch apart, and afterwards at the 
distance of thirty-eight inches. At the first position the one 

• Phil. Mag., p. 88, July 1837. 



Intelligence and Miscellaneous Articles. 15 

tenth cubic inch of hydrogen was yielded in 4-5", at the second 
position in 210". Testing the same phsenomenon by the 
needle, the first position gave a permanent deflection of 60°, 
and the second of 45°. By the first method the difference 
detected was equal to the value of the difference between 45 
and 210, or 165. By the second, the difference was equal to 
that between 60 and 45, or 15. Had the divisions of the 
needle galvanometer been in seconds, or in thirds, or even in 
tenths of degrees, its indications would still have been inferior 
in delicacy to those which the watch and meter thus afforded, 
with the utmost precision and facility. 

72. It will appear subsequently that this superior precision, 
readiness and certainty, do not constitute the only advantages 
presented over the magnetic needle, and are not the only rea- 
sons why this particular method of experimenting should be 
preferred. 



XI. Intelligence and Missellaneous Articles. 

THE HERSCHEL DINNER. 

WE deem it proper to record briefly in this Journal the circum- 
stances attendant on the recent festival in honour of Sir John 
F. W. Herschel, and in commemoration of his return from Southern 
Africa, after having executed a minute astronomical survey of the 
Southern Hemisphere, in accordance with the intention and in fur- 
therance of the design of his illustrious father. A meeting of the 
leading men of science and officers of various scientific institutions 
in the metropolis having taken place in the apartments of the Geolo- 
gical Society, at a time when the arrival of Sir J. Herschel in his 
native land was daily expected, to consider and arrange the best 
means of giving him that welcome with which every lover of know- 
ledge was eager to greet him, it was resolved that a pubhc dinner 
should be held on the occasion, to which he should be invited, and 
a vase of silver, to be purchased by the subscriptions of the friends 
of science, presented to him. Forty-six Stewards were appointed, 
including several noblemen distinguished by their patronage of 
science, or their connexion with scientific institutions ; His Royal 
Highness the Duke of Sussex, K.G,, P.R.S., having consented 
to take the Chair, and R. I. Murchison, Esq., F.R.S., V.P.G.S., 
was appointed Honorary Secretary. The following is a list of the 
Stewards : 

H, R. H. THE DUKE OF SUSSEX, K.G., P.R.S., in the Chair. 

STEWARDS. 

His Grace the Duke of Northumberland, K.G., F.R.S. 

The Marquess of Lansdowne, K.G., F.R.S. 

The Marquess of Northampton, V.P.R.S., F.G.S. 

The Earl Fitzwilliam, F.R.S., F.S.A. 

The Earl of Burlington, V.P.R.S., Chancellor of the Univ. Lend. 

The Bishop of Norwich, P.L.S., F.G.S. 
Airy, G. B., F.R.S., Astron. Royal. I Baily, F., Treas. R.S., P.R.A.S. 

Babbage, C, F.K.S., Luc. Prof. Camb. 1 Beaufort, Capt., R.N.,F.R.S.,F.R.AJ5. 



76 Intelligence and Miscellaneous Articles. 



Broderip, W. J., F.R.S., F.G.S. 
Brodie, Sir B. Bart., F.R.S., P.R.C.S. 
Brown, R., F.R.S., V.P.L.S. 
Buckland, Prof., D.D., F.R.S., F.G.S. 
Children, J. G., V.P.R.S., F.S.A. 
Christie, S. H., Sec. R.S. 
Colby, Col. R.E..F.R.S.,Dir.Trig.Surv. 
Cole, Viscount, M.P., F.R.S., F.G.S. 
DanieU, Prof.,F.R.S. 
DeMorgan, A., Prof., Sec. R. A.S. 
Egerton,SirP.,Bart.,M.P.,F.R.S.,F.G.S. 
Faraday, Prof., D.C.L.,F.R.S. 
Fitton, W. H., M.D.,F.R.S., V.P.G.S. 
Gompertz, B., F.R.S., P.M.S. 
GreenouRh, G. B., F.R.S., F.G.S. 
Gilbert, Davies, V.P.R.S., F.R. A.S. 
Halford, .Sir H., Bart., F.R.S., P.H.C.P. 
Hamilton, W., F.R.S., P.R.Geogr.Soc. 
Holland, H., M.D., F.R.S. 



Jones, Rev, R., Prof. King's Coll. Lend. 
Konig, C, K.H., F.R.S., F.L.S. 
Lemon, Sir C, Bart.. M.P., F.R.S. 
Lubbock, J. W., F.R.S., F.R. A.S. 
Lyell, C, F.R.S., V.P.G.S. 
Macl^ay, W. S., F.L.S. 
Murchison, R. I., F.R.S., V.P.G.S. 
Peacock, Prof., F.R.S., F.R.A.S. 
Powell, Prof., F.R.S. 
Rennie, G., F.R.S., F.G.S." 
Rigaud, Prof., V.P.R.S. 
Roget, P. M., M.D., Sec. R.S.,F.R.A.S. 
Sedgwick, Prof., F.R.S., F.G.S. 
Smith, Joseph, F.R.S., F.L.S. 
Smyth, Capt., R.N.,K.S.F.,For.Sec.R.S. 
Somerville, W., M.O., F.R.S., F.L.S. 
Taylor, John, F.R.S., Treas. G.S. 
Walker. J., F.R.S., P. Civ. Eng. 
Whewell, Rev. W., F.R.S., P.G.S. 



The Herschel Dinner took place accordingly on Friday the 15th 
instant, when upwards of four hundred noblemen and gentlemen 
were assembled, including a large proportion of the most eminent 
cultivators of science, in all its departments, and of literature and the 
fine arts, from all parts of the kingdom. Their distinguished guest 
was seated on the right of the President, who was supported on his 
left by the Marquess of Lansdowne and Earl Fitzwilliam. After 
dinner His Royal Highness addressed the company on the occasion 
of the festival, and presented Sir John Herschel with the vase, which 
had been placed on the table by Mr. Murchison, and in which were 
deposited several sheets of paper containing the autograph signatures 
of the persons present. Sir John Herschel returned thanks in a most 
interesting address delivered with deep feeling and replete with ap- 
propriate reflections. Speeches were afterwards made by Professor 
Sedgwick, Sir Thomas M. Brisbane, Admiral C.Adam, the Marquess 
of Lansdowne, Professor Rigaud, the Earl of Burlington, Sir Wil- 
liam R. Hamilton, the Rev. W. Whewell, P.G.S. , the Marquess of 
Northampton, the Earl Fitzwilliam, and R. I. Murchison, Esq., Hon. 
Sec. The last speaker in returning thanks for the stewards, assigned 
as the reason why he, a geologist, had taken so active a share in the 
arrangements for this festival, that the distinguished astronomer, in 
honour of whom it was held, himself claimed the character of a 
geologist ; and he concluded by saying : " May it ever be the pride 
of our hearts to repeat, ' I was one of those who welcomed Herschel 
to his native land.' " 

Of the Noblemen included in the list of Stewards His Grace 
the Duke of Northumberland only was absent, and his absence we 
regret to learn was occasioned by a severe attack of illness. We have, 
however, great pleasure in adding, that the cost of reducing Sir 
John Herschel's observations in the Southern Hemisphere will be 
defrayed by the princely munificence of this nobleman. 

The Vase is a splendid copy of the Warwick Vase, in silver, 
placed upon a pedestal of black marble, on each side of which will 
appear an inscription in silver relief. That proposed for the prin- 
cipal place, from the pen of H. Gaily Knight, Esq., M.P., is as fol- 
lows: 

" Herschel ^'wwiori ab Afris reduci 
Ccelis australibus exploratis." 



Intelligence a7id Miscellaneous Articles. 77 

In every point of view, whether as regards the just claims of Sir 
John Herschel on the regard of every lover of science, or the claims 
of science itself on the estimation of the public, the Herschel Dinner 
must be considered as one of the most interesting and successful 
meetings ever held to promote the triumphs of intellect and social 
virtue. It is with great satisfaction that we have understood that 
the rank of a Baronet of the United Kingdom has since been con- 
ferred upon the illustrious object of this festival. 



ACTION OF LIGHT ON SOLUTION OF CYANOGEN. 

MM. Pelouze and Richardson have read a memoir on this subject 
to the Institute, in which they observe that the knowledge which 
chemistry possesses on the above-named subject is very incomplete. 
M. Vauquelin was occupied with it in 1818, and showed, that besides 
ammonia and a peculiar black substance, there were formed by the 
action of cyanogen upon the elements of water, three distinct acids, 
namely, carbonic and hydrocyanic acids, and another which he con- 
sidered as composed of cyanogen and oxygen. His opinion as to the 
nature of this last substance was entirely founded on theoretic views, 
for he had not separated his new acid, nor studied any of its combi- 
nations. The experiments of MM. Pelouze and Richardson show 
that M. Vauquelin was in error in announcing the formation of 
cyanic acid by the decomposition of cyanogen in water, and the 
substance which he supposed to be cyanate of ammonia was a mix- 
ture of urea and oxalate of ammonia. 

An aqueous solution of cyanogen, prepared in the usual manner, 
was exposed to the action of light, until the odour of cyanogen ceased. 
The solution had a strong smell of hydrocyanic acid ; its colour was 
slightly yellowish, and it was neutral. In the lower part of it a 
light, black, flocky substance was separated. It was collected in a 
filter, and freed by distilled water from foreign soluble matter. After 
this purification it was but slightly soluble in water and in alcohol, 
insoluble in aether, but on the contrary dissolved by acetic acid and 
the caustic alkalis, and with bases it formed true salts. 

The authors had not so much of this substance to subject to 
analysis as they could have wished, but they are of opinion that its 
true composition is expressed by the formula Az« C^ H'< O**. 

Part of the liquor was submitted to ebullition, and the vapour dis- 
engaged was passed into lime-water. An abundant precipitate of 
carbonate of lime was formed, which left no doubt as to the formation 
of carbonic acid during the decomposition of cyanogen in water. 
The remainder of the liquor jdelded during concentration a very 
sensible quantity of ammonia and hydrocyanic acid. The dried 
residue had a distinct yellow tint, and a sharp saline taste. Put 
into alcohol it was divided into nearly equal portions ; the soluble 
portion possessed all the characters of urea ; the residue insoluble in 
alcohol was oxalate of ammonia. 

The authors state that the analysis and minute examination of 

• In this notice the original formulae are preserved. 



78 Intelligence and Miscellaneous Articles. 

these two substances leave no doubt in their mind as to their pro- 
duction during the spontaneous decomposition of cyanogen when 
dissolved in water. If M. Vauquelin had pursued the examination 
which he had commenced in the products of this reaction, he would 
perhaps have first made the admirable discovery, which was effected 
fifteen years afterw^ard by M. Woehler, of the artificial production of 
animal matter. 

It is extremely curious to observe a substance of comparatively 
simple composition, such as cyanogen, give rise to so many diflferent 
products by its reaction on water. 

Admitting Az^ C^ H« O^ [O* ?], as its composition the decompo- 
sition of cyanogen in water may be explained by the following equa- 
tion: 

1 atom of Urea Az* C'^ H^ O^. 

3 do. Hydrocyanic Acid .... Az'^ C H'^. 

4 do. Carbonic Acid C* 0«, 

1 do. Ammonia Az^ H^. 

1 do. Oxalate of Ammonia . . Az^ C'^ H** O*. 
1 do. Black Substance Az* C^ H^ O*. 



Az22 C22 H36 0»8. 

L'Institut, March 1838. 



BICHROMATE OF PERCHLORIDE OF CHROMIUM.* 

This remarkable compound was discovered by Berzelius ; it was 
at first called perchloride of chromium, because when put into contact 
with water it was changed into chromic and hydrochloric acids. Its 
true composition was ascertained by M, Heinrich Rose. 

M. P. Walter gives the following process for preparing this com- 
pound : put into a tubulated glass retort an intimate and finely 
powdered mixture of 100 parts of fused common salt, and 168 parts 
of neutral chromate of potash ; an S tube is to be put into the tubulure 
of the retort, through which there are gradually poured 300 parts 
of concentrated sulphuric acid. The action is rapid from the com- 
mencement ; intense red vapours, accompanied by much chlorine, are 
disengaged. ITie receiver is to be kept cold to condense the vapour. 
The acid must be gradually added, or otherwise a loss of the red 
vapours will take place, and besides this the contents of the retort 
rise and pass into the receiver. As soon as the acid is added, the 
retort is to be gently heated, and the heat is to be increased until 
yellow vapours begin to arise ; the operation is then finished. In 
the receiver there is found a liquid of an intense red colour, and a 
solid substance, which, according to M. Dumas, is a compound of 
this substance with chlorine. By decantation they may be sepa- 
rated, and the liquor when rectified, so as not to obtain the whole of 
it, yields a compound, the boiling point of which is constant. 

The liquid thus obtained is of a magnificent blood-red colour ; it is 
volatile, and yields fumes abundantly ; when put into a quantity of 

* See Lond. and Edinb. Phil. Mag., vol. xii. p. 83. 



Meteorological Society. 79 

water it falls to the bottom in drops of an oily appearance, and is con- 
verted into chromic and hydrochloric acids. Its boiling point is 244° 
Fahr., and its specific gravity is 1*71 ; it acts rapidly on mercury ; it 
is decomposed by sulphur, detonates with phosphorus, dissolves chlo- 
rine and iodine, and combines with ammonia with the disengagement 
of light. A small quantity mixed with concentrated alcohol com- 
bines with it with violent explosion, and the inflamed alcohol is pro- 
jected with force. This unexpected action had nearly deprived M. 
Walter of his eyesight, and burnt him horribly. 

The analysis of this substance by M. Walter agrees with that of 
M. Rose, namely. 

Oxygen 19-28 

Chlorine 45*14 

Chromium 35-58 100' 

Ann. de Chimie. et de Physique, 66-391. 
It appears to me that it would be more simple to consider this 
compound as an oxichloride of chromium, than a bichromate of per- 
chloride of chromium. . It might then be regarded as composed of 
Two equivs. of Oxygen. ... 16 or 20 
One equiv. of Chlorine . . 36 — 45 
One equiv. of Chromium. .28 — 35 

80 100 
R. P. 

METEOROLOGICAL OBSERVATIONS FOR MAY 1838. 

Chisunck. — May 1. Fine: rain: fine at night. 2,3, Very fine. 4. Dry 

haze. 5. Thunder : fine. 6. Slight haze : very fine. 7, 8. Very fine. 

9. Hot and very dry. 10. Cold and dry. 11,12. Fine. 13. Hazy: fine. 

14. Cloudy and cold. 15 — 18. Fine. 19. Overcast. 20. Slight rain. 

21. Cloudy. 22,23. Cloudy: rain. 24. Overcast. 25 — 27. Fine. 
28. Rain. 29,30. Fine. 3J. Very fine: heavy thunder-showers at night. 

Boston. — May 1. Cloudy: heavy rain p.m. 2. Cloudy. 3. Cloudy: 
thunder, lightning, and rain early a.m. 4,5. Fine. 6. Cloudy. 7 — 12. 
Fine. 13. Cloudy : rain early a.m. : rain p.m. 14. Cloudy: rain early a.m. 
15 — 17. Fine. 18— -19. Cloudy. 20. Cloudy : rain p.m. 21. Cloudy. 

22. Cloudy : rain a.m. 23. Rain. 24, 25. Cloudy. 26, 27. Fine. 28. 
Fine: rain p.m. 29. Cloudy. 30. Cloudy: rain p.m. 31. Cloudy. 

Applegarth Matise, Duvifries-shire. — May 1. Sun shone : hoar frost a.m. : 
cold P.M. 2. Sun shone : genial rain afternoon. 3. Sun shone, showery 
a.m. 4. Sun shone : moist and mild : genial. 5. Sun shone : a beautiful 
day. 6. Sun shone : very dry and parching. 7. Sun shone : warm and 
genial. 8. Sun shone : very warm and clear. 9. Sun shone : the 

same. 10. Easterly wind : cool. 11. Sun shone: milder than preceding 
day. 12. Sun shone : a few drops of rain p.m. 13. Sun shone: 
withering day. 14. Sun shone: cold, with hail showers. 15. Sun shone: 
clear and cold. 16. Sun shone : heavy hail showers, 17. Sun shone: 
cold and showery. 18. Sun shone: cold and withering. 19. Cold and 
very wet. 20. Heavy rain all day. 21. Sun shone : showery and mild. 
22, Mild and very wet. 23. Sun shone : moist: rather cold. 24. Sun 
shone : clear growing day. 25. Sun shone : mild and clear. 26. Sun 
shone : clear and warm. 27. Dull and withering. 28. Sun shone : clear 
and warmish. 29. Soft air : wet all day. 30. Sun shone : warm and 
growing. 31. Sun shone : mild with showers. 









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THE 

LONDON AND EDINBURGH 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



T 



[THIRD SERIES.] 



AUGUST 1838. 



XII. On the Co7iditions of Equilibrium of a Homogeneous 
Planet in a Fluid State. By James Ivory, X'.fl'., F.R.S., 

HIS problem is treated in the Traite de Mecanique of 
Poisson, a work which is in everybody's hands ; and, in 
order to abridge, I shall take the differential equation of a 
level surface from that work (Equat. (b), p. 536, vol. ii. edit. 
2nd,) viz. 

X.dx-\-Ydy-\-Zdz-\-a^{xdx + ydy) = 0: 

here ^, 3/, z are the rectangular coordinates of a point in the 
level surface, z being parallel to the axis of rotation : X, Y, 
Z, are the attractions of the whole mass upon the particle, in 
the respective directions of cc,y,z'. and a is the angular velo- 
city of rotation about the axis. By integrating the foregoing 
equation we obtain, 

Const. = r^Kdx + Ydy -^Zdz)+ ^ G^'+/) ... (1.) 

The whole mass being divided into two parts by ^he level, 
surface, I shall put P, Q, R, for the attractive forces parallel 
to ^, y, z, which the matter within the level surface exerts 
upon the particle in that surface ; and P', Q', R' for the like 
attractions of the matter without the level surface : so that we 
shall have 

X = P + P', Y = Q + Q', Z = R + R'; 

and the equation of the level surface will be 

* Communicated by the Author. 
Phil. Mag, S. 3. Vol. 13. No. 80. Aug. 1838, G 



82 Mr. Ivory om the Equilibrium of ajiuid Planet. 

Const. = fiFdx + QcZj/ + R dr.) + -^ {^^ + f) 

+ r(?<dx + Q'd7/+ R'dz). 

Now the least attention to the nature of this equation will 
show that the attraction of the matter without the level sur- 
face is entirely independent of the rest of the equation. As 
there is no definite relation between P, Q, R and P', Q', R', 
these functions denoting the attractive forces of different 
quantities of matter, a level surface will have no determinate 
figure, unless we divide its equation into two separate parts 
containing the unrelated quantities, viz. 

Const. = r{Pdx+Qdi/+Rd%)+ ^{x^+f) (2.) 

Const. :=r{P'dx + Q'di^ + R'dz) (3.) 

Such are the equations of equilibrium of a homogeneous 
planet supposed fluid : but it will be more convenient to use 
the two following, of which equation (1.) is the sum of (2.) 
and (3.), 

Const. = fiXdx +Ydi/+Zdz) + -^ i^^+f) — (1-) 

Const. = nF'dx -{-Q'd 7/+ R'dz) (3.) 

Now these two equations are the same with those given in 
a paper in the Philosophical Transactions for ] 824, and in 
two subsequent papers written for the purpose of obviating 
some objections (I had almost said, frivolous objections) of 
M. Poisson*. The foregoing very simple investigation proves 
the justness of the solution of the problem in the papers 
cited ; and at the same time shows the insufficiency and in- 
correctness of making the figure of equilibrium depend on 
one equation. (Poisson, Mecanique, p. 550, vol. ii., edit. 2nd.) 

What is said is sufficient for the present purpose : but the 
subject deserves a more extended discussion ; because, by the 
procedure here followed, the greatest simplicity and clear- 
ness are introduced in one of the most perplexed and imper- 
fect theories, that occur in the system of the universe. 

July 10, 1838. James Ivory. 

* See Phil. Mag., First Series, vol. Ixiii. p. 339; vol. Ixv. p. 241 ; vol. 
Ixvi. p. 429; vol.lxvii. p. 31, 82, 439.— Edit, 



[ 83 ] 

XIII. On a Property of the Conic Sections. By J. W. Lub- 
bock, Esq.*. 
IF any hexagon be circumscribed about any conic section, 
and the opposite angles be joined, the three diagonals 
have a common intersection!. 

This remarkable theorem was first given by M. Brianchon 
in the 13th cahier of the Journal de VEcole Polytechnique, 
p. 301. It was deduced by M. Brianchon through Pascal's 
celebrated property of the inscribed hexagon, but it seems 
desirable to obtain a direct proof of this curious theorem, 
and in so doing I have found an equation of condition be- 
tween the coordinates of the angles of the circumscribed 
hexagon, upon which the property in question may be said to 
depend. 

Let the angles of the circumscribed hexagon be denoted by 
the figures 1, 2, 3, 4, 5, 6, as in the annexed diagram. The 
lines 1 4, 3 6 and 2 5 have a common intersection. 



Let «, /3 be the coordinates of the intersection of the line 
1 4 with 2 5 then, Xi,y^ being the coordinate of the point 



X. —X. 



^ ^ (^4.^1 -3/4^1) (-^2 -'%) + (■^5.^2-3/5 -^2) (-^1— -^4) 
(j/l-3/4)('^6-«^2) + (^2-^/5) {^\—^^) 

and if a, jS are also the coordinates of the intersection of the 
lines 1 4 and 3 6, so that the lines 1 4, 2 5, and 3 6 have 
a common intersection, 

^ _ { ^^y^—y^ ^1) (■^3— -^e) + {^^yQ—y^Vo} (^i— -^4) 

(^1—3/4) (^3-^6) + (3/6-3/3) (^l-~'^4) 

* Communicated by the Author. ,^ — ~^^^ 

t On this subject see also a paper by Mr. Davies, Phil. Mag., First 
Series, vol. Ixviii. p. 337.— Edit. 

G2 



84 Mr. Lubbock on a Property of the Conic Sections. 

Equating these values of a, we obtain the following equation 
of condition, upon which the truth of the theorem in question 
depends, 

C^i— 5^4) { (^s-^e) (^5i/2— 3/5 ^2) + (^5—^2) {^6^3-2/g ^3) } 

+ (^2— 5^5) { (-^i —•^4) (^65^3-^6 -^3) + (-^6— -^3) (^4^1 -3/4 ^1) } 

= 0. 

It remains to prove 'that this equation does hold good, in 
consequence of the relations which exist between the quan- 
tities contained in it. 

We may make Xi = 0, .Tg = without limiting the gene- 
rality of the theorem, the direction of the coordinate axis y 
being any whatever ; this amounts to taking for the origin the 
point in which the line 1 2 touches the parabola. In this 
case the points 5 and 4, 6 and 3, 1 and 2 are symmetrical 
and similarly involved, and the preceding equation of con- 
dition becomes 

(3/1 — .2/4) -^5 {-^3 (3/2-3/6-) + -^6(3/3-3/2)} 
+ ( 3/2—3/5) ^4 {^6 {2/1 -3/3) + -^3 (3/6-3/1) } A. 

+ (3/3-3/6) •^4 ^5 (3/2-3/1) = 0- 

The equation to the tangent of the parabola j/^ — p x pass- 
ing through the points (2, ?/) («, jS) is 

p[x—oif-^y[x-'a){y-^)-\-^x{y-^f = B. 

If x,y coincide with the point 2, so that Xc^ = 0, and if 
a, /3 coincide with the point 3, 

SMarly x« = iMfcg.) . 

Again, if in the equation B the point (^,j/) coincide with 
the point 3, the two values of —— ^ correspond to the direc- 
tions of the lines 3 2 and 3 4. 



^ _ 23/3 + ^"Z yi~px^ 



3/3-/3 jp 

Making a = a^g = 0, i3 = ^2 > ^^^ taking the upper sign 

^ - (3/3-3/2) (2j/3-2 ^ yi-'^y^{y^-y'^ 

= ^.^2(3/3-^2) ^g {jeforg^ 
V 



Mr. Lubbock on a Property of the Conic Sections, 85 

Taking the lower sign and making a, /3 coincide with the 
point 4. 

"'4 — 1^ * 

4 p 

Similarly, because the points (5, 4), (6, 3) and (1, 2) are sym- 
metrical, 

^ _ ^{yG-yi){yo-y6+yi) 

b p 

Again, by equation B, 

x-a; = (-^-3/4) {^.^4 ± 2 a/ 3/4^-/? ^4} 

if the upper sign refer to the direction of the line 4 5, the 
lower refers to the direction of the line 4 3. 

r - ^ (i^4-i/3 + 3/2) (.^5-3/4 + .^3-3/2) 

Equating this value of x^ to that found above, 

(3/4-3/3+3/2) (3/4-3/3 +3/2+^5) +(^6-3/1) (3/5-3/6+ 3/1) - 

,j 0, 4-w - 3/5 ± ^3/5^-^ (3/6-^1) (3/5-3/6+3/1) 

y\~yz'^y'i— 2 • 

Hence y^—y^ + 3/2 is equal to 3/5-3/6 + yi, or to y^-y, . 
Employing the values of o^g, ;i"4, Xc^ and j;g which have been 
found, and the remarkable equation of condition 

3/4-3/3 +y2=y6 = ^6+ ^1 or 
3'i-3/2 + 3/3-3/4 + 3/5—3/6 = 
it is easy to verify the truth of the equation A, p. 84. 
This equation may now be put in the form 

(3/1 -3^4) (3/6-3/1) (3/3-3/2) (3/4-3/3+3/2) {3/2 (3/2-3/6) +3/1 (3/6-3/1)} 
+ (3/2-3/3) (3/3-3/2) (3/6-3/1) (.3/4-^3+3/2) {3/1 (3/1-3/3) +3/2 (3/3-3/2)} 
+ (3/3-3/6-) (3/3-3/2) (3/4-3/3+3/2)' (3/6-3/1) (^2-3/1) 

= (3/6-i/O (3/3-^2) (3/4-3/3+3/2) {(5/1-^4) {3/2(3/2-3/6) +3/1 (3/6-3/1)} 

+ (3/2-3/5)13/1 (3/1 -3/3) +3/2 (3/3-3/2)} +(3/3-3/6) (3/4-^3+3/2) 

(3/2-3/1)} 

putting for ^2—^/5 its valueyg— 2/4+^,— ^g, the quantity be- 
tween the brackets becomes 

(3/1-3/4) {3/2 (^2-^6) +yi (y6-3/r)i-^ 

+(^3-3/4+3/1-3/6) {yi (yi-y3)+3/2 (y3-y2)} 

+ ( 3^3-3/6) ( ^4— y3 +- ^2) (3/2—3/1) ^-^ 

= (yi-3/4) {3^2 (3/2-3/6) +yi (^6-3/1) +yi (yi-3/3) +3/2 (3/3-5^2)} 



86 Mr. D. Waldie's Experimental Researches 

+ {ys—ys) {yx {y\-y3)+yAy3-y^)+iy4-y3+y^) iy^—yx)) 
= (yj-yJ iy^-ye) iy^-yx) + (ys-ye) iyx-y^) iyx-y^) 

= , which proves the truth of the theorem in question. 

If yi-ya + 2^2 = ye-yx 
ys-ye + yi = ya-y^ 

^4 = oTg , ^4 = ^5 J the points 4 and 5 coincide, and by 
reference to the figure it will easily be seen that it is useless 
to coincide this case. 

The equation of condition 

yx -y-i + ^3-^4 + y^-ye = o 

has been found upon the supposition, that Xi = 0, x.^ = 0, 
which simplifies the expressions. But it is easy to show by 
the transformation of coordinates that if the above equation 
be true, with such limitations, it is also true in the more ge- 
neral case, the only limitation required being, that the axis x 
be parallel to the axis of the parabola ; and then, however 
the circumscribed hexagon be situated 

yi-y^+ya-yi+ys-ye = o- 

In the Phil. Mag. and Annals, N.S., 1829, vol. vi. p. 249, 1 
gave a direct proof from the equation to the parabola y^ z^px 
of Pascal's celebrated property of the inscribed hexagon, 
and I showed that the proof might be extended to the general 
equation of the conic sections y"^ z=z p' x -\- q' a?^, by substi- 
tuting for the coordinates x and y of any point 

X- — , 

-; — ~- and . , respectively. 
p +q' X p +q X ^ "^ 

By such substitutions all the preceding expressions which 
are true for the parabola y'^ = px may be extended to the 
conic sections generally, which are included under the equa- 
tion y^ — p' x-\-q[ x^. Thus the equation of condition 

yx-y'i + ^3-^4 + ^5-^6 = becomes 

yx y<i ,_ ys , ^^ \ y^ ^_ ■ 

p' + q'xi pf-Vq^x^ p' + ^^s y + ?'^4 P^ + Q.'^^ P'-^9.'^6 

XIV. Experimental Researches on Combustion and Flame. 
By David Waldie*. 

[Illustrated by Plate I.] 

nPHE subject of combustion has long engaged the attention 

-*- of the most distinguished chemists, and the results of 

their inquiries are incorporated more or less in the various 

* Communicated by the Author. 



laru^. £■ I'cli*t T-Ail. Ma^j Voi MIT Fl. /. 



/ 3 



M 



n 












A 



I / 



^i^> A? 



ij 




^Vf.J. 




Slructwre^ of J'tcuTvejy CU.iMtra^zJ'e of M^ Jiiild^'s 



on Combustion and Flame. 87 

treatises on chemistry ; an excellent account of them may be 
found in Ure's Chemical Dictionary, under the article Com- 
bustion. The subject however is not exhausted, and there 
are still some questions which- by a new method of investiga- 
tion may I think now be decided, and several phaenomena 
hitherto unaccounted for which may now be explained. 

The principal or essential circumstance in combustion is 
the fact of combination between two substances of opposite 
electrical energies. One of these, as being the apparent source 
of the heat and light, is called the combustible ; the other, as 
absolutely necessary to the phaenomena, the supporter of 
combustion. This has given rise to the division of bodies 
into these two classes, supposed by some to be remarkably 
distinguished from each other by their part in the process as 
they are in their place on the electro-chemical scale. Others 
again have contended that there is no essential distinction be- 
tween the two classes of bodies with respect to this phaeno- 
menon ; that in fact both are equally entitled to the name of 
combustible, and that the heat and light evolved are simply 
indications of energetic chemical action between any two sub- 
stances : in proof ol" this various instances have been adduced, 
such as the combustion which takes place between iron or 
copper filings and sulphur, between potassium and cyanogen 
or sulphuretted hydrogen, between vapour of anhydrous sul- 
phuric acid and dry baryta, as noticed by Bussy, magnesia and 
sulphuric acid, &c. in all of which we have all the phaeno- 
mena of combustion, without the presence of any of those 
substances exclusively called supporters of combustion, or 
in some of these cases without either combustibles or sup- 
porters. 

The latter explanation seems now to be admitted so far by 
chemists in general, but yet it occurred to me that its truth 
was susceptible of still better demonstration, and that instead 
of searching for particular instances of combustion it might 
be supported by a much more general proposition : that in 
fact if this were the true explanation, it should follow as a ge- 
neral rule, that if what is commonly called a combustible burn 
in a supporter, a supporter ought also to burn in a com- 
bustible. This accordingly on trial I found to be the case. 

The apparatus employed for these experiments consisted 
of a wide-mouthed flask (about 8 or 9 inches long) having 
cemented to it a cap of tinned iron, pierced with four holes : 
to two of these two brass sockets were soldered, made to fit 
the ends of two flexible tubes proceeding from two gas- 
holders ; to the two other holes were attached small pieces 
of tube, over one of which a piece of sheet caoutchouc was 



B8 Mr. D. Waldie's Experimental Researches 

tied, through which a slender platinum or iron wire could be 
passed to try the temperature of different parts of the flame, 
and to the other was fixed a bladder in order to allow of ex- 
pansion. The flask was filled by being immersed in a trough 
of water ; the water was then displaced by inserting one of the 
flexible tubes into one of the sockets, and causing gas to flow 
into it from a connected gas-holder, the water escaping by 
the other socket ; the tube was then removed, corks inserted 
in the sockets, and the flask placed on a retort stand, with its 
mouth downwards and the bladder hanging flaccid : the tube 
was then replaced in the socket so as to supply more gas if 
necessary. Now when the flask was filled with one of the 
common supporters, such as oxygen, and one of the common 
combustible gases was to be burnt in it, the method requires 
no explanation. When again the oxygen was to be burnt in 
hydrogen the cork was removed from the socket, and the gas 
set fire to, being made to flow gently from the flask, in order 
to prevent the combustion from getting inwards ; the oxygen 
then being made to flow with a proper degree of force from 
a small brass jet fixed on the end of another flexible tube, 
communicating with another gas-holder containing oxygen, 
was passed steadily through the burning hydrogen into the 
flask, and the end of the flexible tube pushed home into the 
socket ; the hydrogen burning outside the flask was now ex- 
tinguished, and the oxygen found burning within. 

When again the gas was not confinable in a common gas- 
holder with water, such as nitrous acid vapour, it was pre- 
pared in a wide-mouthed flask ; and when this was believed 
to be full, a jet of hydrogen burning from a brass nozzle 
fixed to the turned-up extremity of a glass tube connected 
with a flexible tube was let down into it : or, for instance 
with chlorine, a jar was filled with this gas over the water- 
trough, and a jet let down as before, a tin plate being fixed to 
the tube so as to cover the jar and allow the jet to descend 
to near the bottom. If again these gases were to be burnt the 
materials were placed in a small flask, to which was fixed a 
tube having a brass piece to fit the socket of the flask, and a 
jet placed on its extremity. 

By means of such apparatus oxygen was made to burn in 
atmospheres of hydrogen, olefiant gas, coal gas, sulphuretted 
hydrogen and carbonic oxide; nitrous oxide was burnt in 
hydrogen and coal gas; nitrous acid vapour in hydrogen; 
chlorine in hydrogen, and mixtures of these with nitrogen or 
carbonic acid, common air for instance, in the same gases. 

By these experiments, oxygen, atmospheric air, nitrous 
oxide, nitrous acid and chlorine are shown to be not only 



on Combustion and Flame. 89 

really but also apparently as much combustibles as hydrogen 
or coal gas, and these again are exhibited in the form of sup- 
porters of combustion. In fact this distinction arises simply 
from the accidental circumstance of oxygen being contained 
in our atmosphere, and of hydro-carbonaceous substances 
being emitted from other bodies into it: there is really no 
distinction between the two, the phaenomena of combustion 
proceeding from the act of combination of the two oppositely 
electrical substances. 

I did not succeed in making iodine vapour burn in hydro- 
gen, nor the reverse ; the affinity for each other seems not 
sufficiently strong. Nitric oxide does not burn in hydrogen, 
nor vice versa ; a circumstance remarkable enough, as the two 
constituents of this gas are in respect to their density in pre - 
cisely similar circumstances to a simple mixture of the two ; 
no more however than might have been expected from the 
circumstance that a mixture of the two does not detonate but 
burns with flame in contact with the air. It is said in some 
works on chemistry, that the products of this combustion are 
water and pure nitrogen : this I suppose must have been a 
conclusion made beforehand, on the supposition that the nitric 
oxide is decomposed completely: it would appear rather that 
the oxygen for the combustion of the hydrogen is supplied 
from the air, and that the nitric oxide is either not decom- 
posed, or at least only partially, as I find copious nitrous acid 
fumes produced, whether the experiment is performed by 
burning them together in a jar even with excess of hydrogen, 
or by burning the mixture from a jet either in oxygen, or oxy- 
gen in it. 

I had made but very few of these experiments until I per- 
ceived that there was a great variety in the appearance of the 
flames. The jet of hydrogen for instance, in passing from air 
to oxygen was observed to shrink in size, and become brighter 
and denser ; the jet of oxygen in hydrogen was observed 
also to be much smaller than that of hydrogen in oxygen. 
The flame of hydrogen in chlorine, nitrous oxide, or nitrous 
acid was much larger than in air ; the flame of these gases in 
hydrogen again was small and concentrated. In all these 
cases the gases were made to issue from the same jet, with 
as nearly as possible equal degrees of velocity. 

Before making any observations on the causes of these dif- 
ferences, it will be necessary to take some notice of the struc- 
ture of flame. This has been studied chiefly in the flame of 
a common candle or jet of coal gas. It consists then, accord- 
ing to observations already made, of, 1st, a dark central por- 
tion consisting of unmixed, unconsumed gas ; 2ndly, a dense 



90 Mr. D. Waldie's Experimental Researches 

very luminous white portion surmounting the dark portion 
which penetrates further up its centre than its circumference ; 
this consists of solid particles of charcoal burning at a white 
heat; 3rdly, a blue cap arising from the bottom and sur- 
rounding the dark portion, extending moreover some way up 
the sides of the white part, this being supposed to be com- 
posed of the gas burning in an undecomposed state; 4thly, an 
envelope of a light blue colour, of a pinkish or lilac shade, con- 
sisting of the proper combustible mixture, this being the 
hottest part of the flame : this part is thinnest at the bottom, 
increasing in thickness to the top where, of course, the heat 
is most intense; and, .5thly, another envelope of a yellowish 
brown colour, chiefly covering the upper part, and consisting 
of unconsumed matter or products of combustion. These 
two latter are not well seen in the flame of coal gas, on ac- 
count of the great size and brightness of the luminous white 
portion. 

The explanation of these appearances is obvious enough : 
the gas issuing from the jet spreads out into the atmosphere, 
till it mixes with a sufficient quantity of oxygen to form a 
combustible mixture; as it ascends, however, it becomes 
strongly heated by the surrounding flame, deposits solid 
charcoal, the combustion of which forms the white part of 
the flame. 

When a jet of coal gas or defiant gas burns in oxygen the 
parts of the flame are all the same, but differing considerably 
in appearance ; the dark portion, the white portion, and the 
blue cap 1, b, «, (Plate I.) fig. 1, are greatly diminished in 
size, looking as it were compressed, the white being how- 
ever more brilliant. The light blue portion again, 2, is 
greatly enlarged, the shell of flame becoming much thicker, 
and the heat is much greater, easily fusing a small platinum 
wire. The yellow tail, 3, also is now perfectly visible. The 
whole flame is also much smaller than in air. These changes 
are due simply to the more perfect combustion produced by 
the oxygen being undiluted, so that the greater part of the 
gas at once undergoes perfect combustion; the diminution of 
size of this as well as of flames in general, in oxygen com- 
pared with air, arising from the circumstance, that in the latter 
the gas requires to penetrate or diffuse itself over a much 
larger space before it meets with a sufficient quantity of air 
to produce full combination. 

In flame again, where there is no solid matter deposited, as 
in that of hydrogen, the appearances are much simpler ; in this 
case (burning in oxygen) it consists of a dark central por- 
tion of unmixed gas, 1, of a light lilac blue envelope of ex- 



on Combustion and Flame. 91 

plosive mixture, 2, and of the external envelope and tail of 
unconsumed matter or products of combustion, 3, often of a 
greenish colour. 

Olefiant gas issuing with the same degree of force and 
from the same jet as hydrogen burns with a much larger 
flame : this is easily explained, as it requires 1 5 times its 
volume of air to burn it, whereas hydrogen requires only 2| 
times. This shows the influence of quantity on the size of 
flames. But hydrogen requires only its own bulk of chlorine 
or of nitrous oxide for combustion, yet its flame in these 
gases is much larger than it is in air ; these burn on the other 
hand with a very small flame in hydrogen. The only cause 
to which this can be attributed appears to me to be the dif- 
ference of their diffusibility. From Mr. Graham's researches 
we now know the law of the diffusibility of gases, — that it 
varies inversely as the square root of their density ; so that 
hydrogen, a light gas, diffuses itself much more rapidly through 
chlorine, than chlorine, a heavy gas, does through hydrogen. 

These then are the two causes by which I would explain 
the different appearances of different flames, and they are 
confirmed by all the experiments I have made. Probably 
they are not the only causes, but they are the primary ones, 
particularly with the simple gases. A great number of experi- 
ments were made to ascertain, if possible, the exact propor- 
tional effect of these two causes, but with the apparatus I was 
in possession of, it was a hopeless task. The only way in 
which I could regulate the jet of gas was by the degree of 
opening of the stop-cock by which the water was supplied to 
the gas-holder, a very imperfect method where accuracy is 
required. With some of the gases produced in the method 
already described there was not even this resource. The 
peculiarities of size, &c. which I notice here, are, however, so 
great and decided, as to leave no doubt about them, allowing 
freely for inaccuracy of the apparatus. 

A few examples may be given in illustration of these re- 
marks. The diffusibility of oxygen to hydrogen is as 1 to 4, 
or the inverse of the square root of their respective specific 
gravities (sp. gr. of hydrogen = 1). The difference of size 
however of their flames is not so great as might be supposed 
from this compared with chlorine : to account for this it is 
to be kept in mind that the oxygen requires twice its volume 
of hydrogen for combustion, so that it must spread further 
through the hydrogen than it would otherwise require to do, 
and thus make its flame larger ; the flame of hydrogen in 
oxygen being smaller than it otherwise would be from the 
same reason. Let us suppose it set down in this way : 



92 Mr. D. Waldie's Experimejital Researches 







Difiusi- Inverse of 


Vols. 


Sp. gr. 


bility. quantity. 


1 


16" oxygen 


1 X 2 = 2. 


2 


!• hydrogen 


4 X 1=4.. 



Now let carbonic oxide be treated in the same way. 
Vols. Sp. gr. DifFus. Inv. of quant. 

1 16- oxygen 3*75 x 2 = 7*5 

2 14<'12 carbonic oxide 4* x 1 = 4* 

In this case the flame of oxygen should be larger than that 
of carbonic oxide (that is, when burning in each other), be- 
cause their diffusibility is nearly equal, and the larger quantity 
of carbonic oxide is required. On trial I found that it was 
so in fact ; the only instance I have seen with unmixed gases 
where the oxygen flame is larger than that of the other sub- 
stance. In the same way the flames of oxygen and sulphu- 
retted hydrogen approximate to each other in size. 

The flames of chlorine and hydrogen in each other ought 
to depend on their diffusibility alone, as their combining pro- 
portion is equal volumes. Not having the chlorine in the 
gas-holder I could not ascertain its size well ; but from the 
trials I have made it is very small, similar to that of oxygen. 
So also is that of nitrous oxide, and nitrous acid has also a 
small flame. The flame of hydrogen in these gases is very 
large, of a greenish or yellowish colour, darkish in centre, 1, 
(fig. 2) brightest and hottest about the middle of the outer 
part, 2, but very diffused in its appearance. 

The flame of oxygen in hydrogen consists of a dark un- 
mixed central narrow portion, 1, (fig. 3) surrounded by a 
lilac blue flame of small size, 2, and then by a dark yellowish 
envelope and tail, 3. The heat is concentrated in the blue 
portion, where the platinum wire fuses and sparkles brilliantly, 
the heat being compressed into so small a space. 

The flame of oxygen in olefiant gas is a very beautiful and 
instructive example. It is necessary to premise, that as the 
oxygen is the least diffusible of the two gases, and as it re- 
quires only one third of its volume of olefiant gas to form a 
proper combustible mixture, both of these circumstances con- 
spire to make its flame small. In this, therefore, we have a 
small light blue flame, darkish in centre ; in this blue flame is 
the strongest heat which fuses the platinum wire, 1 and 2, 
fig. 4 ; surrounding this and stretching far above it was a 
dull strong yellow flame, h, red at the edges and dark in the 
centre, 3, evidently consisting of solid red hot charcoal, a 
very large quantity of which was separated as smoke, and 
adhered to the sides of the flask. 



on Combustion and Flame. 95 

Gases were also mixed with nitrogen and carbonic acid. 
When a pure gas was burnt in such a mixture it had its 
flame much enlarged, as it had to expand itself further till it 
met with a sufficient supply of the other, on account of its di- 
lution. Thus hydrogen, as already noted, burns with a larger 
flame in air than in oxygen, and oxygen with a very large 
flame in hydrogen diluted with twice its bulk of nitrogen or 
carbonic acid. When mixed with the gas which was to issue 
from the jet an opposite effect was produced ; thus the mix- 
ture of nitrogen or carbonic acid with hydrogen burnt with 
a smaller flame in oxygen than pure hydrogen did, and air 
burnt with a much smaller flame in hydrogen than oxygen did 
— there being less gas issuing — and of course sooner meet- 
ing with a sufficiency of hydrogen. In this case the flame of 
air was such as represented in fig. 5, burning from a wide 
hole in a piece of a tobacco pipe : 1, dark ', 2, blue very di- 
stinct ; 3, dark reddish tail ; 4, greenish envelope. 

Carbonic acid was employed in these experiments, in order 
that its effects might be compared with those of nitrogen, on 
the supposition that, on account of its greater density, a jet of 
gas burning in it would be expanded or diffused to a greater 
degree than in a similar mixture of nitrogen; this accordingly 
was found to be the case. The greater degree of contrac- 
tion which should be supposed to take place when the mixed 
gases were made to issue from the jet was not demonstrated 
so clearly by the experiments ; in some instances it seemed 
sufficiently apparent, in others it was doubtful. Experiments 
with more accurate apparatus would be necessary to establish 
the proportional effect of such mixtures. 

These experiments were made on the idea that from them 
we should get an explanation of the fact, that carbonic acid 
is more deleterious to combustion than nitrogen, or " exerts 
a positive influence in checking combustion, as appears from 
the fact, that a candle cannot burn in a gaseous mixture com- 
posed of four measures of atmospheric air and one of carbonic 
acid." (Turner's Elements, sixth edit.). On examining the 
effect of nitrogen on the combustion of a jet of coal gas, it 
was found that by successive additions of it to air the flame 
became more and more expanded, the tube of flame becoming 
wider and longer, and the white part diminishing or disap- 
pearing altogether when the nitrogen was in considerable 
excess; when beyond a certain proportion, it would not burn 
at all, obviously from the cooling [effect produced by excess- 
ive diffusion. It was therefore concluded, that this effect 
depended on the density of the gases, and accordingly on 
trial the following results were obtained. 



04 Mr. D. Waldie's Experimental Researches 

Combustion of coal gas in mixtures of 

Sp. gr. 
Permitted. Prevented. IIydrog.-=.\. 

1 Oxygen... 7 8 Nitrogen 14<'12 

1 Do. ... 3 4 Muriatic acid ... 18-4.2 

1 Do. ... 2i 3 Carb. acid 22-12 

1 Do. ... 2 2i Fluosilic acid ... 52-72 

Now we observe that their power of preventing combustion 
is just in the order of their density. Sulphurous acid was 
also tried, but it was found to hold about the same place that 
muriatic acid did, which it should not do, as it is denser than 
carbonic acid, itssp.gr. being 32-1 (hydrog. = 1). It ap- 
pears, however, that it is decomposed when there is more 
than a certain proportion of oxygen present to invigorate the 
combustion ; as on inspecting the flame the external blue shell 
of flame, where the principal combustion takes place, was 
found to be enlarged and considerably .stronger in colour, 
and a red streaky appearance was also observed in the flame, 
precisely similar to that observed in the flame of sulphuretted 
hydrogen, from separation, I believe, of particles of sulphur ; 
this being in accordance with the fact, that hydrogen and 
carbon at a temperature of ignition decompose sulphurous 
acid. 

Sir Humphry Davy tried the effect of various mixtures of 
gases in preventing the explosion of oxygen and hydrogen, 
a table of which he has given. To many of these this ex- 
planation does not apply, as the greater part of those he em- 
ployed were combustible gases ; and there is most probably 
in that circumstance other causes affecting the result, only to 
be avoided by employing incombustible gases. He has 
noticed, however, that a wax taper is extinguished in air con- 
taining yo^^ °^ silico-fluoric and ^th muriatic acid gas ; also 
that a larger quantity of steam is necessary to prevent the ex- 
plosion of oxygen and hydrogen than of nitrogen. This 
latter fact is usually connected by chemical writers with the 
heat necessary to maintain steam in the state of gas, but 
it appears rather to be one instance among the others fol- 
lowing the general law; that, of ijicombustible gases 'which 
remaiti undecomposed the ponxter of preventing combustion is in 
the order of their density: what the exact ratio is I cannot at 
present say, but beginning with steam, which has a sp. gr. 
ss 9. (Hydrog. = l)j we have the gases increasing in this 
power in the order already given in the table, namely, nitro- 
gen, muriatic acid, carbonic acid, and fluosilicic acid. The 
vapour of anhydrous sulphuric acid, sp.gr. = 40*1, should 
stand between the carbonic and fluosilicic acids, if no decom- 



on Combustion and Flame. 95 

position takes place ; this I have not yet tried. TJiis effect of 
density in cooling the Jlame depends on the excessive diffusion 
qfthejlame in the denser gas. 

The effect of diffusibility on a flame burning in another 
gas is obvious enough, for it is visible ; but when the gases 
are mixed together in one vessel its influence is not so easily 
perceived. It appears to me, however, that in this case it 
operates in a similar manner: in passing an electric spark 
through an explosive mixture, or applying a heated body to 
it, the combination and combustion take place amongst the 
particles immediately in contact with the exciting cause, and 
are thence propagated to the rest of the mixture; when the 
gases are pure, this takes place so rapidly as to appear in- 
stantaneous; but if they be diluted with another gas, the pro- 
gress of the flame may be easily seen. In a mixture which 
does not explode by the electric spark, I conceive that the 
particles of the combustible mixture immediately subject to 
the influence of the spark do combine, but that being diffused 
to too great a degree, either from excessive dilution or from 
excessive diffusibility in a denser gas, the temperature is re- 
duced so much that it does not cause combination of the rest 
of the mixture. This idea seems to be confirmed by the fact 
(Turner's Elements, sixth edit., p. 252), that " An explosive 
mixture diluted with air to too great a degree to explode by 
electricity, is made to unite silently by a succession of electric 
sparks," namely, from new particles of the mixture coming to 
be subjected immediately to the action of the spark. This view 
is likewise supported by other considerations. 

In the table I have given fluosilicic acid does not seem to 
be so powerful as it should be, but this probably depends on 
impurity. These experiments would require to be repeated 
on a larger scale, as mine were performed with a jar capable 
of containing only about 4 oz. of water, and a still smaller 
trough, with 6 or 7lbs. of mercury. 



These researches throw complete lighten the action of the 
blowpipe : the jet of air thrown into the central cool part of 
the flame is in precisely the same circumstances, and has ex- 
actly the same appearance as a jet of air burning in the flask 
containing a carburetted hydrogen gas, except of course in 
being surrounded by a hot external flame, and therefore im- 
proved by this circumstance. In this case we see the two 
phaenomena at once, the vapour burning in the air, and the 
air burning in the vapour. Hence also the reason why the 
flame of the blowpipe is so distinct when thrown through this 



96 Mr. D. Waldie on Combustion and Flame, 

part of the flame, and so different when projected on the upper 
part, where the gas being ah'eady mixed with air it can act 
only as a mechanical agent. 

This may be seen very well with sulphur. A crucible of 
moderate size was filled to about one third with sulphur, and 
placed on a charcoal fire till it boiled. A jet of oxygen flow- 
ing with a certain force was introduced within the upper part 
of the cavity of the crucible, entirely within the blue burning 
flame of the sulphur outside; a strong yellowish tapering flame 
was observed, darkish in centre, and red at edges and tail, of 
about one inch in length. The same experiment was repeated 
with the same circumstances, substituting air for oxygen; a 
very slender jet of blue flame was observed darkish at centre, 
and red at the tail, greatly smaller than that of the oxygen. 
These flames are of course expanded by the heat of the va- 
pour to double their volume, but their relative size is in ac- 
cordance with the principles already laid down. 

The influence of quantity is also well seen when diluted 
gases are burnt from a jet. Thus 1 oxygen and 8 nitrogen 
or carbonic acid will not burn in the flask filled with hydro- 
gen from the brass jet commonly used, nor even from the to- 
bacco pipe, but will do so from the mouth of the flexible tube 
about one-fifth inch diameter, forming a thin blue hollow cone 
of flame, fig. 6 ; sometimes this cone was deficient at the top, 
and was extinguished when the gas was made to flow with 
greater velocity. 

In these cases when the diluted gas issues from a small 
orifice the heat produced from the combustible mixture of the 
gases is so little that it is cooled by the velocity of the cur- 
rent ; from a larger orifice it comes more slowly, and the small 
quantity of combustible mixture formed constitutes the thin 
shell of flame observed. 

These then seem to be the primary causes regulating the 
size and appearance of flames, hitherto, so far as I am aware, 
unobserved or undescribed. Probably, however, these are 
not the only causes, particularly with compound gases. I 
have made a few observations on these, and have observed 
some peculiarities, in nitrous oxide for instance; to these 
however I shall not advert until they have been examined 
more particularly. One peculiarity in the flame of hydro- 
gen must have been frequently observed, namely, a green 
jet inside of the usual dark central portion ; and when the 
flame is full, a dark central part even in this. Having 
only unsupported conjecture to offer in explanation of this, 
I shall refrain from saying anything at present. There are 



Professor Forbes's Researches on Heat. 97 

also peculiarities of colour and appearance of the external 
envelopes and tails so often referred to, which might be worth 
examining. 

These remarks have, I trust, thrown some additional light 
on the nature of gaseous combustion and the influences affect- 
ing it. The inquiry seems to be worth the prosecuting, in 
order to obtain accurate results. For this purpose superior 
apparatus is required: one most essential instrument is a gas 
reservoir, from which gas can be expelled with any de- 
gree of force that may be required, and with considerable 
accuracy. The flask I may also remark, though it may do 
very well for most flames, does not suit well those which re- 
quire a large and free supply of the atmospheric gas ; thus 
olefiant gas will scarcely burn in the flask full of air : it 
shakes violently as if seeking for air, and then goes out ; and 
this cannot be remedied by forcing in air, as the agitation 
thereby produced blows out the flame. By pursuing the in- 
vestigation with greater accuracy, results may probably be 
obtained that may assist in elucidating the nature and af- 
fections of gaseous bodies. In the mean time I shall prosecute 
the inquiry as much as lies in my power, [with the view of 
giving greater accuracy to the results already obtained, or 
making new observations connected with the subject. 

Linlithgow, June 2, 1838. 

XV. Researches on Heat. Third Series. § 1. On the un- 
equally Polarizable Nature of different Kinds of Heat. 
§ 2. On the Depolarization of Heat. §3. On the Refran- 
gibility of Heat. By James D. Forbes, Esq., F.R.SS. 
L. 8^ E.f Professor of Natural Philosophy in the University 
of Edinburgh.* 

[Illustrated by Plates II. & IV.] 

§ I. On the unequally Polarizable Nature of different Kinds 

of Heat. 
T has been my anxious wish to preserve these papers pure 
from even the appearance of controversy, and those who 
have paid attention to the recent history of our present sub- 
ject must be aware that without making direct allusion to the 
doubts which have at different times been thrown upon my 
experiments, I have contented myself with adducing new facts 
and more convincing reasonings ; and I have had the satis- 
faction to see that the general result of this course has been 

* Read before the Royal Society of Edinburgh 16th of Apiil 1838: 
abridged by the Author from the Transactions of that Society, vol. xiv. j 
and communicated by him. 

PhiL Mag. S. 3. Vol. 13. No. 80. Aug, 1838. H 



I 



98 Prof. Forbes's Researches on Heat. 

the gradual abandonment of such doubts, and the entire 
adoption of my conclusions. 

I believe that only a single exception remains to this state- 
ment. I expressed my belief in my Jirst paper that heat was 
differently polarizable, according to the source whence it was 
derived. M. Melloni* failed to verify this result, and the 
opposite conclusion, namely, that all kinds of heat are equally 
polarized by a given pile of mica, was prominently put forth 
by himself and M. Biot as an important discoveryf. With- 
out any undue confidence in my first, confessedly imperfect, 
researches, I proceeded in my second paper :j; to give what 
I considered ample proofs of the correctness of the state- 
ment, though the great dissimilarity of the numbers arrived 
at from those of my first paper, showed that the latter were 
worthy of very little confidence on the ground of numerical 
exactness, which, indeed, I never claimed for them. The 
later experiments, however, were made with a view to accu- 
rate results, and I stated certain forms of the experiment 
which I had devised on purpose to meet the objections of 
M. Melloni, although I avoided mentioning his name. 

It seems, however, that M. Melloni, returning to the subject 
with his accustomed diligence, after receiving my second 
paper, still confirmed his former results, and he has attempted 
to show, in a very long paper, published in the Annales de 
Chimie ifor May 1837 (which only appeared in October), that 
his results must be exact, and the probable source of my 
errors. I contented myself with giving a very brief answer 
to this paper in the Philosophical Magazine for December 
1837, admitting the improbabiHty that so experienced an 
operator as M. Melloni should be wrong in his numerical re- 
sults, but stating convincing grounds for believing that his 
explanation of my conclusion, founded on experimental errors, 
was inapplicable. The inquiry which I have since been led 
to make, and the entirely satisfactory explanation at which I 
have arrived of a difference so puzzling, terminating in a con- 
firmation of my original statement, I now proceed to detail. 

I have not the remotest intention of examining and critici- 
sing M. Melloni's paper in the Annales de Chimie for May 
1837} as respects trifling or personal matters, which I readily 
confide to the impartiality of those best qualified to judge : 
but it is quite necessary to state the facts which I had ob- 
served, and M. Melloni's mode of accounting for them. 

With two polarizing mica bundles of great tenuity, pre- 

* Comptes Rendus de PAcademte des Sdeiwes, ii. 140. f Ibid. p. 194. 
X Lond. and Edinb. Phil. Mag., vol. xii. p. 549 et teq. 



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Tliird Series. — Variable Polarizahility of Heat. 99 

pared in the method described *, marked I and K, I found 
that, with heat from an Argand lamp, 72 to 74 per cent, of 
the incident rays were polarized, that is, — of 100 rays trans- 
mitted when the plates were parallel, 72 to 74- were stopped 
when one was crossed or its plane of refraction turned through 
90°. With heat from boiling water, but 44 per cent, were 
polarized, and heat from sources of intermediate intensities 
gave intermediate results. 

M. Melloni ingeniously argued that this appearance might 
arise from the circumstance that the mica bundles becoming 
most heated by those kinds of heat which they absorbed most 
readily, or transmitted least easily (viz. heat of low tempera- 
ture), the pile was continually receiving a supply of heat by 
secondary radiation from the mica, which, having no relation 
to the parallel or crossed positions of the plates I and K, of 
course tended to diminish the apparent polarization of the 
heat, or to equalize the effect in the two positions. 

The supposed effect of secondary radiation from plates had 
been so often urged against my experiments, that, though as 
often proved to be insignificant or insensible, it gave me no 
surprise to see it started afresh, and in so plausible a manner. 
M. Melloni was probably not aware that the screen for inter- 
cepting the heat was placed between the source of heat and the 
polarizing plate K, (as shown in PI. II. fig. 2,) so that the mica 
plates were only absorbing heat during the exceedingly short 
time (10 seconds) of one swing or dynamical impulse of the 
needle, otherwise I do not think he would have urged so in- 
finitesmal an objection f. I endeavoured, however, to meet 
it directly in this way. I took two mica bundles, G and H, 
and placed them parallel, as shown in fig. 3. But instead of 
placing the pile at P, where it receives at once the directly 
transmitted heat from S (the screen being removed), and the 
supposed secondary radiation of the surface ab of the mica 
plate, I placed it at p, identically situated with respect to the 
surface a b, but wholly removed from the influence of direct 
radiation from S. When this experiment was performed with 
dark heat (which, according to Melloni, ought to give the 
greatest effect) not the slightest movement of the galvanometer- 
needle was observable on removing the screen, during a far 
longer space of time than is ever in practice allowed for the 
absorption of heat. This experiment ought to be considered 
quite conclusive. 

• Lond. and Edinb. Phil. Mag., vol. xii. p. 650. 

t I might add, too, that, had he been aware of the extreme tenuity of 
the mica plates employed (of which more hereafter), he must have been 
led as a necessary consequence of his own reasonings to admit that the 
effect must be insignificant. — Ann. dc Chimie, Mai 1837, p. 13, note. 

H2 



1 GO Prof. Forbes's Researches on Heat. 

M. Melloni had hinted that the different dimensions of the 
sources of heat, and the various angles under which the rays 
fell on the mica plates must materially affect the results ; and, 
as I was quite convinced that operating with parallel rays was 
the most correct method, I proceeded to repeat my experiments 
on his plan, with a salt lens placed in front of the source of 
heat so as to render the rays parallel ; I also removed the 
polarizing and analysing plates to a considerable distance 
from the pile, and afterwards varied their distance in order 
to see whether any adequate explanation of the discrepancy 
could thus be obtained. 

The apparatus was arranged in the following way:— A 
rock-salt lens was placed between the source and screen 
(fig. 2 above) so that the heat was refracted into a nearly 
parallel beam before incidence upon I and K, which were 
removed to a distance of more than a foot from the pile ; the 
distance of the source being 2 feet. 

The apparent polarization was somewhat increased, as 
I had anticipated, from the rays falling more nearly at a con- 
stant angle when previously rendered parallel ; but the dif- 
ferent polarizability of the different kinds of heat was even 
more distinctly marked than ever ; whilst the distance of the 
mica plates from the pile was now such as to reduce to insig- 
nificance any effect of secondary radiation, had such before 
been sensible. 

In prosecuting these experiments, most of which were re- 
peated many times under various circumstances, I remarked 
more distinctly than formerly the influence of particular states 
of combustion of the source of heat upon the index of po- 
larization, and the accidental variations to which this gives 
rise on different days, and even during the progress of an 
experiment. Heat from brass about 700° I have generally 
found the most uniform on different days, though there occa- 
sionally occurs in a series of experiments, considerable devia- 
tions from the mean. The Locatelli lamp seems subject to 
greater variations, and the Argand still more ; indeed, I have 
found it so impossible to maintain an Argand lamp in a uni- 
form state of combustion, even for a quarter of an hour, that 
I have lately abandoned the use of it. But the quality of 
the heat from incandescent platinum varies between the widest 
limits. Nor is this wonderful ; it is composed of heat from 
two very different sources combined in uncertain proportions, 
that from the incandescent coil of wire, and that from the 
alcohol flame which heats it. The intensity of incandescence, 
too, varies exceedingly. On one occasion, when the incan- 
descence was unusually bright, and the alcohol flame very 



Zon^ ^ A'ciuc, TAU: J/a^^ FcL II, 



Ftff /. 





Irof. Forbe,f ',s Ji^feoifX?tc-s on.- Heebt^ TA>>d fSeries. 



Third Series, — Variable Polarizahility of Heat. 101 

low, I obtained a higher degree of polarization than I have 
ever done before or since. The ordinary proportion between 
the indications with I and K parallel and crossed^ is with in- 
candescent platinum 100 to 26 or 27. In this case it was 
100 ; 20 ; and when the heat was lifted by an interposed plate 
of thin glass, it rose as high as 100 : 13. 

The general results obtained in the way above described 
are stated in the following table, in which I have included the 
numbers for mercury heated to 410°, and for boiling water 
taken from the second series* ; those experiments not having 
been repeated because the use of a lens is in those cases of 
little avail. 

Polarizing Plates I and K. 

Source of heat. Rays out of 100 polarized. 

Argand lamp 78 

Locatelli lamp 75 to 77 

Incandescent platinum (usually) 74 to 76 

Incandescent platinum, with glass '06 inchl 

thick, interposed, 6 to 7 per cent, more, or J 

Alcohol flame 78 

Brass heated to about 700° 66'6 

Ditto, with a plate of mica '016 inch thick "i 

interposed, (between ^K and B) J 

Mercury in a crucible at 410° 48 

Boiling water 44 

I presume that it will be conceded, that the experiments 
now cited, incontrovertibly establish the unequal polarizability 
of heat from different sources. Yet, I confess, I should have 
felt uneasy, could I have thrown no light upon the cause of 
the discrepancy between M. Melloni's results and my own. 
This I believe, that I am able completely and satisfactorily 
to do, allowing him every credit for the perfect exactitude of 
his experiments. For the sake of clearness, I will state the 
course by which I myself arrived at this result. 

It occurred to me, that it would be satisfactory for the 
further and independent confirmation of the conclusions just 
given (which were then only partially obtained), to examine 
the index of polarization (by which I mean the per centage 
of the heat stopped in the crossed position of the polarizing 
and analysing plates) deducible for different sorts of heat, 
from a series of experiments made wholly without reference 
to this question, I mean those on depolarization, considered 
in another section of this paper, and which, it will be seen by 

* vol. xii. p. 551. 



102 Prof. Forbes's Researches on Heat. 

a reference to the mode of reduction there employed, required 
to be recomputed in order to give the index of polarization. 

I at first imagined, that the experiments made with each of 
the three kinds of heat then employed (Argand lamp, incan- 
descent platinum, and dark hot brass) would give throughout 
the same result for the same kind of heat. This was far from 
being the case ; the interposition of the depolarizing plate of 
mica between the polarising and analysing plate, acting simply 
by transmitting only certain rays of heat, had modified the 
index of polarization, and that more or less, as the thickness 
of the interposed mica was more or less considerable. Such 
a result might have been anticipated, as in exact conformity 
with the discovery I had formerly made ; but I was misled 
by a false notion, w^hich I had heedlessly adopted, and suf- 
fered to remain unquestioned, that, in order to affect the in- 
dex of polarization, the heat must have been modified by 
transmission prmo2/5 to its falling upon the first or polarizing 
plate, whilst, in the experiments referred to, the modification 
took place between polarization and analysation *. Of course, 
when I perceived this oversight, the confirmation of my views 
was greater, because it was unforeseen. 

But the most material result of the examination of those 
experiments was this. By a reference to the section on de- 
polarization, it will be seen that five different thicknesses of 
mica (varying from three to sixteen thousandths of an inch) 
vf&ce interposed successively, and the index of polarization 
determined for each of the three kinds of heat. Now, upon 
examining the result of these fifteen experiments, I clearly 
perceived (amongst occasional irregularities) this law to pre- 
vail, — that whilst aJilTn of mica "003 inch thick scarcely altered 
the characteristic properties of heat from different sources, as 
shown by their variable indices of polarization, an increased 
thickness of mica had almost no sensible effect upon the heat 
from the Argand lamp, but it increased the index of polariza- 
tion of dark heat so fast, that, with a thickness of mica of '016 
inch interposed, the apparent index of polarization for heat 
from the Argand lamp, incandescent platinum, and dark hot 
brass, was almost the same. 

When I had fully seized this conclusion, the explanation 

• Lest this confusion should, by possibility, occur to any one, as it did 
to myself, I will observe that the position of the sifting or modifying plate, 
absorbing the least refrangible rays, is quite immaterial, provided it occur 
between the source and the indicator of heat jfor whether the rays in ques- 
tion are absorbed before or after polarization, those which ultimately 
escape and reach the pile are the only ones of which the index of polari- 
zation is measured. 



Third Series* — Variable Polarizability of Heat. 1 OS 

of M. Melloni's results was easy and complete. It appears 
from the account of his experiments, that he still employs 
piles of mica of the form I at first used, consisting of distinct 
laminae separated by a knife, then laid together and united at 
the edges, up to the number of 30, 60, and even more*. On 
the other hand, the piles 1 and K, which for two years and a 
half I have employed, are of a degree of tenuity really sur- 
prising. The mode of their construction I mentioned briefly 
in my last paper, art. 20, and it is so very superior to any 
other, that it is probably from inadvertence that it has not 
been generally employed. The piles laminated by the action 
of violent heat, afford a multiplicity of parallel surfaces in a 
given thickness of mica, which no mechanical method can 
approach. The actual thickness of mica which they contain, 
I am unable accurately to estimate. The plates marked G 
and H are much thicker, perhaps twice as thick as those 
marked I and K, which I commonly use ; yet the former, as 
I roughly estimate by the tint they give in polarized light, 
are only about one thousandth of an inch in thickness. At 
the utmost, the plates I and K can be but one fifteen hun- 
dredth of an inch ; and yet it appears that their polarizing 
power (depending solely on the number of surfaces they con- 
tain) is equal to M. Melloni's pile of ten distinct plates placed 
at the same angle (35° to the incident rays). The mean 
thickness of the elementary plates can, therefore, be only one 
fifteen thousandth of an inch; and they reflect abundantly 
the colours of Newton's rings. 

Now, I have found by the depolarization experiments, that 
it requires a much greater thickness of mica than that tra- 
versed by the heat in passing through the plates I and K 
(even allowing for the obliquity) to affect materially the index 
of polarization of heat from different sources, such as from 
brass at 700°, and incandescent platinum. It is, therefore, a 



* Annates de Chimie, Mai 1837. At p. 17, &c. M. Melloni has given a 
minute account of that method of constructing the piles, which, " amongst 
several different ways, he considers the preferable one." No one could 
doubt from his language that he is describing a new and improved form 
of the apparatus. I regret for a moment to descend to notice an apparent 
want of justice and courtesy towards myself; but it is im[)ossible for me to 
not to observe, that the procedure he so exactly details, is, to almost the 
minutest particular, identical with that which I myself used in June 1835, 
in constructing, in M. Melloni's presence, the first pair of piles used for 
polarizing heat which existed in France, at a time when M. Melloni ex- 
pressed his unqualified scepticism as to the polarization of heat generally; 
which piles I left, at his desire, where I presume they now are,— in his own 
possession. This mode of construction I soon after abandoned, for the 
improved one alluded to in the text. 



104 Prof. Forbes*s Researches on Heat. 

necessary consequence of the construction, that the heat passes 
through such piles as I use unaltered, or nearly unaltered, 
in its character, whilst in passing through bundles of de- 
tached plates laid together, the thickness of mica to be tra- 
versed is sufficient to modify the heat by absorption, in such a 
way that the difference of quality has vanished, whatever he the 
source, in the very act of transmission. It it hardly likely, con- 
sidering the size of M. Melloni's mica plates (4 inches long 
and 2 wide), that they could be less than one fifteen hundredth 
of an inch thick each ; a pile of ten would then be ten times 
as thick as my pile of equal energy, and at an incidence of 55° 
the thickness traversed would not be much shorter than that 
of the mica plate alluded to in art. 20, which we have there 
seen to be sufficient to obliterate all distinctive character as 
to polarizability between an Argand lamp and dark heat. 

Being now fully aware of the importance of the construc- 
tion of piles of mica which I had adopted, I thought it worth 
while to examine the proportions of heat from different 
sources, which these very delicate laminae were capable of 
transmitting, which, I presumed*, would be found far less 
variable than when plates of the usual thickness are employed. 
My expectations were more than realized, as is seen in the 
following table, the second column of which shows the pro- 
portion, to the whole incident heat, of that transmitted by the 
two mica piles I and K placed parallel to each other ; by far 
the greater proportion of the loss being that due to the obli- 
quity of reflection and the number of surfaces f . By way of 
contrast, I have placed in the third column the proportion 
of the whole incident heat transmitted at a vertical incidence 
by a plate of mica '016 inch thick. 

Rays out of 100 transmitted by 

Source of Heat. Plates I and K Mica plate '016 

parallel. inch thick. 

Locatelli lamp .... 18*8 51 

Ditto, with plate of glass '06 \ i /^.o 72 

inch thick interposed . . J 

Incandescent platinum . . 17*6 50 

Dark hot brass (700°) . . 15-5 15 

Heat from boiling water .10* 8 

It is very evident that, for the first four sources of heat at 
least, the transmissive power of the plates I and K varied 

* I do not state this as a new idea ; it has been repeatedly remarked 
by M. Melloni, that, in proportion as substances are thinner, they possess 
a more equable diathermancy for heat of different qualities. 

t The part of the effect due to reflection, I had previously established to 
be nearly the same for different kinds of heat. 



Third Series. — Variable Polarizahility of Heat. 105 

little, and in no sort of proportion to the characteristic action 
of mica even in moderate thicknesses. This will be more 
evident, if we compare the ratios of the heat from different 
sources transmitted in the two cases, taking the heat from 
the lamp sifted by glass as the standard for each column. 

Plates I and K. Mica -016 inch. 

Locatelli with glass . . 100 100 

Locatelli 116 79 

Incandescent platinum .108 70 

Brass at 700° .... 96 21 

Heat of 212° .... 62 11 

I need hardly add, that so remarkable a result as that the 
heat sifted by glass should be less readily transmitted by the 
thin mica laminae, than the direct heat from a lamp, was care- 
fully verified. 

Since, then, the first four kinds of heat are transmitted 
without any great difference of proportion, by the piles I and 
K, and since, especially, the heat from a lamp sifted by glass 
and that from dark brass possess almost exactly similar cha- 
racters in this respect, it is very clear that we have a new 
ground for rejecting as untenable M. Melloni's supposition, 
that the apparent differences of polarization in my experi- 
ments, arose from the unequal proportions of heat absorbed 
by the mica piles when the source varied. 

Admitting, then, the fact of the variable index of polariza- 
tion exhibited by heat of different qualities similarly treated, 
we are tempted to inquire what explanation can be offered 
of it. This question, inferring for its answer a knowledge 
of the nature of heat, we are not prepared to answer with 
confidence. My former suspicion of its being due solely to 
the difference of the refractive index of mica for heat of dif- 
ferent kinds, I am disposed to retract as inadequate, or at least 
to suspend my judgement respecting it. I at one time thought, 
that, supposing the mica bundles unequally permeable to heat 
from different sources, a difference of ratio in the total heat 
reaching the pile with the plates I and K^ parallel and crossed 
might be accounted for. But a careful analysis of the cir- 
cumstances convinced me, that the absorptive action, if as- 
sumed the same for common and polarized heat, could pro- 
duce no such effect. One of the most plausible suppositions 
which occurred to me was this, — that, supposing the reflec- 
tion of luminous heat to take place more copiously at the 
mica surface than that of dark heat, and supposing the angle 
of incidence to be that of total polarization, since the refracted 
ray contains as much heat (if heat be like light) polarized 
perpendicular to the plane of incidence, as is reflected and 



106 Prof. Forbes's Researches on Heat. 

polarized in the plane of incidence, the ratio of the polarized 
to the total heat transmitted would be greatest in the heat of 
highest temperature. Unfortunately for this theory, careful 
experiments assured me that heat from different sources un- 
derwent the same, or nearly the same, intensity, of reflection 
under the same circumstances. 

We are, therefore, led to regard this character of unequal 
polarizability, as probably indicating a difference of character 
of a fundamental kind between heat and light ; at least a super- 
added quality or peculiarity of vibration, which becomes more 
and more sensible as heat is removed in its character from 
light, or has (as we shall hereafter see), generally speaking, a 
lower degree of refrangibiiity. A sensible undulation, normal 
to the surface of the wave, would of course satisfy this condi- 
tion. I am far from saying that my experiments warrant such 
a conclusion. I am aware that it is inconsistent with the ideas 
entertained by some ingenious speculators upon the nature 
of heat * ; but this very circumstance has led me to bestow 
the greater pains upon establishing the phaenomenon in an 
incontrovertible manner. 

§ 2. On the Depolarization of Heat, 

In the first series of these researches, § 4, I entered pretty 
fully into the subject of depolarization. The establishment 
of the fact was of the highest importance, since there is little 
probability of proving in any more direct manner the doubly 
refractive energy of crystals with respect to heat. But, be- 
sides the demonstration of the fact, I pointed out in that 
paper the important numerical determinations to which it 
might lead ; determinations of the first consequence to the 
theory of heat, and the discrimination of heat from light. The 
measure of depolarization in the case of light, or the quantity 
of light which has become polarized in a new plane by passing 
through a doubly refracting plate, such as mica, depends, 
1. upon the length of a wave of light; and, 2. upon the retar- 
dation which one of the doubly refracted pencils of light suf- 
fers, upon the other, in passing through the mica, which re- 
tardation differs with the material of the plate, varies directly 
as its thickness, and may also vary with the quality of the inci- 
dent ray. 

Hence, as a little reflection clearly shows, if the quantity of 
light (or, by analogy, of heat) depolarized by a plate of given 
thickness be numerically estimated, we may, if the length of 
the wave be given, determine the retardation, or energy of 

« Kelland on Heat, art. 166. 



Third Series. — Depolarization of Heat. 107 

double refraction ; or, if the latter be assumed or known, we 
may find the length of a wave. Considering the latter ele- 
ment as the more important, and not being then in possession 
of any more direct mode of determining it numerically, I 
proposed to assume the retardation due to double refraction 
as the same for heat as in the case of light, (considering heat 
as but less refrangible light), and to determine the length of 
a wave in the way which I fully explained in the First Series, 
art. 68-75*. 

Two circumstances require notice by way of precaution. 
The first is, that, for the very reason that we have periodical 
colours in the case of light, there are different thicknesses of 
mica and different measures of retardation, which, for the 
same length of a wave, will give the same measure of depo- 
larization; these dubious cases (which the formula of depo- 
larization completely expresses) must be distinguished. The 
second remark is, that all our sources of heat furnishing he- 
terogeneous rays, each has its own period of maximum and 
minimum intensity, just as in the case of solar light, and 
since our means of numerical estimation embraces the sum 
of all the effects of heterogeneous rays, we cannot expect re- 
sults which shall rigorously satisfy a formula, in which homo- 
geneity (or constancy of A, the length of a wave), is assumed, 
but consider the approximate result as representing the mean 
or predominating character of the heat employed. 

Recalling, then, Fresnel's formula, quoted in art. 70 of the 
First Seriesf , we have 



p5- = sm^ 180^ 



'° f-r } 



where F* is the intensity of the whole incident polarized ray ; 
E^ the intensity of that portion which, after transmission 
through the depolarizing plate, is capable of being analysed 
in a perpendicular plane. These two quantities being deter- 
mined from observation, the first side of this equation, or 
their ratio, becomes known. On the second side we have 
two quantities, either of which may be assumed, and the 
other becomes known, viz o—e the retardation of the one 
doubly refracted ray upon the other within the crystal, and 
A the length of a wave. Now, it is obvious from the form of 

o—e 
the expression, that an infinite number of values of will 

A 

satisfy the equation; in light there can be little ambiguity 
arising from this cause, because the phaenomena of periodic 
colours at once afford the means of selecting the true solu- 

• Lond. & Edinb. Phil. Mag., vol. vi. p. 366. f liid., p. 367. 



108 Prof. Forbes's Researches on Heat. 

tion. In the case of heat, we must proceed with more cau- 

tion, the value of being wholly unknown ; we only af5- 

sume (as we are entitled to do) that this quantity increases 
uniformly with the thickness of the plate, which it necessarily 
must, since the retardation is as the thickness, and A is inde- 
pendent of it. By a very simple process, the true value was 
easily selected. 

Five depolarizing mica plates, of different thicknesses, of 
exactly the same quality, and each as uniform as possible, 
were provided. They were cut to the same size, and of such 
a form that each could at once be placed with its neutral axis 
(aline in the plane passing through the two axes of double re- 
fraction) vertical, or inclined 45° at pleasure. Their thickness 
was next to be determined. The examination of the colours 
shown by polarized light was the most obvious method, but not 
susceptible of the exactness which was required. It was, how- 
ever, used as a check. 

The following were the results of actual measurement, 
made by means of a pair of callipers constructed for such 
purposes by Troughton. These results are the mean of ten 
measures each, which were rendered difficult by the elastic 
and fissile nature of the substance. 

Thickness in parts 
of an inch. 

No. 1 -0026 

No. 2 -0044. 

No. 3 -0074 

No. 4 '0060 

No. 5 ; • • • '^^^'^ 

With these mica plates in succession, employed for depo- 

larizing, I proceeded to determine the ratio -p^- (p. 107) for 

the most part exactly in the way described and illustrated by 
an example in art. 71, First Series, which I found preferable 
to any other. This laborious investigation I performed for 
heat from three sources ; (1.), an Argand lamp with glass 
chimney; (2.), incandescent platinum; and, (3.), brass heated 
(not to visible redness) by an alcohol flame. The thickness 
of the plates No. 3. and No. 4. being very nearly the same 
(and giving, as they ought to do, almost exactly the same 
measure of depolarization), I preferred using the united thick- 
ness of Nos. 2. and 3. as an interpolation between Nos. 3. 
and 5. The swings of the needle, or dynamical effects, vol. xii. 
p. 547, were always observed, and are alone given. The po- 
larizing and analysing plates were the same marked I and K, 
before fully described (vol. xii. p. 550), and a plate is said to 



Third Series. — Depolarization of Heat. 



109 



be at 0° or at 90° as its plane of refraction is vertical or 
horizontal. With these explanations, and a reference to art. 
71, First Series, the following specimens of observations will, 
it is hoped, be intelligible. 

Argand lamp: 16 inches from centre of pile, depolarizing 
mica plate No. 3. 



Position of Polar, 
izing Plate K (I 
being always at 0°). 


Position of 

Neutral Section 

of Mica. 


Galvanometer. 

Dynamical 

Effect. 


Total Po- 
larization 

F2. 


Depolariza- 
tion 

E2. 


AtO° 
At 90° 

At 0° 


At0° 


o 

11-9 \^ 
3-45^ 
8-8 '^ 
6-75^ 

12-1 ? 
3-75 ? 
8-8 / 
6-7 ^ 

3-7 ^ 

Means 


8-45 


+5-35 
-5-35 
+ 5-05 
-5-35 


At 45° 




AtO° 


8-35 


At 90° 


At 45° 


AtO° 




AtO° 


8-35 


At 90° 




8-38 


5-27 



The following experiment was made with heat wholly un- 
accompanied by light, and with the same mica plate. 

Dark hot brass : 14 inches from pile, depolarizing mica No. 3. 



Position of Polar- 
izing Plate K (I 
being always at 0°), 


Position of 
Neutral Sec- 
tion of Mica. 


Galvanometer. 

Dynamical 

Effect. 


Total Po. 

larization 

r2. 


Depolariza- 
tion 
E2. 


AtO° 
At 90° 


At0° 


5-25 > 
2-0 < 
5-75 ^ 
2-15 V 
5-95 < 
1-95 < 
5-75 ^ 
2-6 v^ 
5-9 < 
1-95 < 
5-65 ^ 
2-3 

5-8 > 
1-8 /> 

Mean 


[3°25]* 


+ 3-75 
—3-8 
+ 3-8 
-3-3 
+ 3-7 
-3-5 


At 45° 
AtO° 
At 45° 


AtO° 
At 90° 




4-0 


AtO° 




AtO°. 
At 45° 
At 0° 


At 90° 
AtO° 
At 90° 


3-95 


4-0 


3-98 


3-64 



* Omitted in the mean as manifestly too small, arising from the lamp 
being just lighted, and the brass not fully heated. 



1 to Prof. Forbes's Researches on Heat. 

It now remains to explain how these observations have 
been discussed. The ratio -^ is at once obtained by divi- 
ding the second mean resuU by the first, and I have purposely 
quoted these observations, to show how very nearly the plane 
of polarization was thrown at right angles by the action of 
this particular thickness of mica, especially in the case of dark 
heat, which appears to be owing to its greater homogeneity, 
as we shall presently have reason to infer. ^ 

We have seen above (art. 32) that 

£2 



pa = sm2 180° 



And therefore. 






sm-\ / E^ 



A 180° 

Since the radical has an ambiguous sign, the equation will be 

O ' c 

satisfied by a value of — — equal to a fractional number «, or 

by 1— a, or 1-f a, or 2— a, or 2 + a, or 3— a, &c. In the 
case of the two examples given above, we have for the Argand 






^=l^ = -e29;\/^^=±'793 



And ^— ^ = -29 or '71 or 1-29 or 1-71, &c. 

A 

j^2 3'64< /E^ 

For the dark heat, ^^ = ^;^ = -915; Y -p2= ± '957. 

And — — = -41 or -59 or r4.1 or 1*59, &c. 

A 

The true value must be such, that, when a number of plates 

o—e 
are employed, — — must increase uniformly with the thick- 
ness of the plates. 

Clearly to mark this, and at the same time to combine the 
results by graphical interpolation, I projected the numbers 
obtained as above in the way shown in Plate II. fig. 1 . On 
a horizontal line spaces representing the thickness of the plates 
were set off as abscissae, and a few of the ambiguous values of 

as ordinates, which are marked by dots. It was then 

easy to select those points thus set ofi^, through which a 
straight line could most nearly be drawn, representing the 



Third Series. — Depolarization of Heat, 111 

linear relation between the thickness of the plate and the 

o^~e 
quantity , (both vanishing when the thickness = 0,) and 

A 

inspection of the figure will show that no doubt can attach to 
the choice of the ambiguous numbers, and also that the straight 
line represents in general remarkably closely the course of 
those points. 

There is one' exception to this statement, and it is an im- 
portant one. It will be observed that the interpolating line, 
instead of passing through any of the dots set off for the mica 
plate No. 3, bisects exactly tisoo dots. These dots are nearest 
to one another in the case of dark heat, — wider apart with 
incandescent platinum, and widest of all in the case of the 
Argand lamp. The explanation is complete and satisfactory. 
The interpolating line in all these cases gives a value of 

o—e . , E^ 

= 1, which gives a value of-™- = 1 ; in other words, 

infers a total polarization of the heat in the horizontal plane 
(or in the case of light total darkness, when the polarizing 
and analysing plates are parallel) which we know can only 
occur when the heat is absolutely homogeneous. The want 
of mathematical coincidence in this case infers the admitted 
physical condition of want of homogeneity in the incident 
rays. Hence, we infer that dark heat is most homogeneous ; 
next, that from incandescent platinum ; and, least of all, that 
from the Argand. 

The proportions give numerical results almost identical for 
the three sources of heat ; a result so far contrary to what I 
expected, that it shows that by this method we cannot hope 
to discriminate the different lengths of waves of these kinds 
of heat, as I had formerly supposed, and shows that the varia- 
tion of A must be very small, or else (what is improbable) that 
it is constantly proportional to the variation of the retarda- 
tion o~e. 

In all the three cases we have as nearly as possible a value of 

l*^ for at a thickness of depolarizing mica, equal to 

A 

•020 inch, or '07 for a thickness of '001 inch. Let us com- 
pare this with the case of light. The sum of the retardations 
for the various mica plates, as given in art. 33, amounts to 
•000199 inch ; the sum of the thickness in the next article is 
•0361 inch, consequently the mean value of the retardation or 
o—e is •OOOOOSS for a thickness of mica of one thousandth 
of an inch. But the length of A for extieme red is '0000266, 



112 Prof. Forbes's Researches on Heat. 

for extreme violet, '000167 inch. Hence for a plate of mica 

•001 inch thick the values of are 

A 

55 
For extreme red light = '207 

^ 266 

For extreme violet light ... -^ — = "329 
° 167 

For heat = '07. 

If we assume the retardation, or o—e, to be the same for 
all lengths of waves, and for heat as for light, we imme- 
diately deduce the value of A, or the length of a wave of heat. 

For since for a plate '001 inch thick, = '07, as above, 

A 

o-e = -0000055, we have 

o — e '00055 «^«^^^ . 1 
A = --— = — - — = -000079 mch, 
•07 7 

about three times as long as a wave of red light, and four and 
a half times that of violet. But it is always to be remembered, 
that this proceeds on the supposition of the retardation being 
invariable. 

I have taken the trouble to calculate and project in a similar 
manner my original observations on depolarization given in 
the First Series of these researches, art. 74, in order that, 
though probably less accurate, they might form a check upon 
the results just given. The plates then employed, and marked 
No. 1 and No. 2, (which are not to be confounded with those 
so designated in this paper) had thicknesses (deduced from 
the retardation) of -0072 and •OOSe inch. I have the gratifi- 
cation to find that the computed results agree almost pre- 
cisely with those just obtained, although from the accidental 
thicknesses of the two plates employed the observations with 
these alone do not enable us to select the appropriate value of 

Q £ 

, there being at least two values which still remain am- 
biguous ; but when taken in conjunction with the observations 
of art. 41, the ambiguity is at once removed, and the nu- 
merical value of A comes out almost exactly as stated above, 
for incandescent platinum and dark heat, and somewhat 
smaller for that of the Argand lamp. 

I desire it to be recollected, that, in speaking of these 
somewhat startling lengths of waves of heat, I am using the 
language of only one of the two hypotheses which serve to 
interpret the results of this section ; for, if the variation be in 
o—e, or the diiFerence of the velocities of the doubly reflected 



Dr. Apjohn on a 7ie'w Compound. 113 

rays in mica, the result would be the same. The experiments 
in a subsequent part of this paper may serve to guide us in 
our choice. Meanwhile, I would observe, that, supposing 
the above results to be explained on the supposition that o—e 
is smaller, instead of A greater for heat than for light, it is 
equivalent to supposing the doubly refracting energy weaker, 
or a greater thickness of a crystal required to produce a given 
effect. Our suggestion respecting the existence of sensible 
vibrations normal to the wave surface (art. 28) will not avail 
us here. For, by the mode of reducing the experiments on 
depolarization, the unpolarized part of the heat does not enter 
into consideration at all * ; consequently those parts of the 
total effect which are due to transverse vibrations alone, are 
not modified by double refraction as so much light w^ould be. 

[To be continued.] 



XVI. On a neno Compound, consisting of Iodide of Potassium, 
Iodine, and the Essential Oil of Cinnamon. By James 
Apjohn, M.D., M.R.I.A., Professor of Chemistry in the 
Royal College of Surgeons, Ireland.^ 

T^HE compound which is the subject of the present com- 
-^ munication owes its origin to an unchemical medical pre- 
scription. A solution of iodine and iodide of potassium in 
cinnamon water having been directed by a physician of this 
city in the winter of 1837, his patient found that during the 
prevalence of very cold weather, the solution, which had been 
previously turbid, became quite clear, and nearly insipid, 
and upon examining the bottle closely he observed deposited 
in the bottom a small quantity of minute capillary cry- 
stals. These crystals were brought to Mr. Moore of Anne- 
street, the apothecary in whose establishment the prescrip- 
tion was made up, and by him to me for chemical exami- 
nation and analysis. Before detailing the means which I 
have employed for determining the exact constitution of this 
substance it will be proper to give the process by which it 
is best procured, and enumerate its leading properties ; points, 
both of which were investigated by Mr. Moore and myself 
conjointly. 

* I do not mean to offer any opinion on the nature of light in a partially 
polarized ray generally ; but, as in the present case, the angle of incidence is 
that of complete polarization nearly, I presume that the transmitted ray 
is undoubtedly composed partly of light polarized perpendicularly to the 
plane of incidence, and partly of common light. 

t Communicated by the Author. 

Phil. Mag. S.3. Vol. 13. No. 80. Aug. 1838. I 



1 1^ Dr. Apjohn oji a new Compound of Iodide of Potassium, 

To a gallon of cinnamon water *, first reduced nearly to 
32°, add four ounces of iodide of potassium and forty grains of 
iodine previously dissolved in a minimum of cold water. Upon 
the instant of admixture the solution becomes quite turbid, 
owing to the production of a yellowish sediment, and this in 
less than a minute becomes crystalline, and then gradually 
subsides. The supernatant solution, which appears almost 
entirely deprived of iodine and oil of cinnamon, is now drawn 
off with a siphon, and the crystals and residual fluid thrown 
upon a single filter, which, when sufficiently drained, is en- 
veloped in several folds of blotting-paper, and transferred to a 
chalkstone, where, by the absorbent powers of the latter and 
the occurrence of spontaneous evaporation, the product is 
rendered perfectly dry and pure. With the quantities stated 
above 60 grains of the compound are obtained. A tempera- 
ture at or very close to 32° is necessary to the success of 
this process. At 40° the brown powder already noticed is 
alone produced, and in much diminished quantity. This 
brown sediment, however, is identical with the crystalline 
product, for it may be converted into crystals simply by re- 
duction of temperature, and I have even found it to undergo 
the same change when collected on a single filter, and set to 
dry on a bibulous stone at the temperature of 45°. 

The crystals are capillary quadrilateral prisms, without 
pyramidal terminations. They are of a beautiful brown or 
bronze colour, and have a strong metallic lustre. Their taste 
is extremely hot and pungent, resembling closely that of oil of 
cassia, but partaking also of that of iodine. In alcohol and 
asther they are readily dissolved, and from these solvents they 
are again deposited with their original appearance upon the 
occurrence of spontaneous evaporation. They are decom- 
posed by water, which extracts from them iodide of potassium, 
and causes the separation of oily drops of a dark colour, which 
are either a mechanical mixture or a peculiar compound of 
iodine and the oil of cinnamon. This action of water, how- 
ever, is greatly diminished when it is close to the freezing 
point, and appears altogether prevented when a certain amount 
of iodide of potassium is present. 

When heated to 82° the crystals melt into a dark liquid, 
from which upon cooling the original substance is reproduced. 
When heated beyond its melting point iodine and a vapour 
smelling strongly of oil of cinnamon sublime, and iodide of 
potassium is left behind, mixed usually with a little carbon 
resulting from the decomposition of a portion of the oil. 

• This water should be prepared by introducii)g into a still one pound 
of cassia bark and two gallons of water, and drawing off one gallon. 



Iodine, and the Essential Oil of Cinnamon. 115 

Starch would appear to decompose this substance, for with 
even its alcoholic or iEthereal solution it forms the well-known 
blue compound. When agitated with water and zinc or 
iron filings, an iodide of these metals is produced, and the 
oil is set free. With mercury the result is the same, and in 
each instance for water alcohol or aether may be substituted. 
Potash also at once developes the oil, forming, as in the case 
of free iodine, iodide of potassium, and iodate of potash. 

From these facts it seems legitimate to infer that it is the 
oil, and not any modification of it corresponding to the ben- 
zoyle of chemists, which is associated with the iodine and 
iodide of potassium, and that they are all held together by an 
extremely feeble affinity, in as much as not only is the iodide 
of potassium separated by water, as has been stated, but 
the iodine is affected by a solution of potash just as if it 
were free. To test the truth of this opinion, a little of the 
compound was decomposed in a small glass retort by the ex- 
act equivalent of a very dilute caustic alkali, and, a receiver 
being applied, about half an ounce of a liquid having the 
appearance and obvious properties of cinnamon water was 
drawn off by distillation. From it, however, I could not, 
though every precaution was employed, procure a particle of 
the original crystalline compound. The properties, indeed, 
of the distilled liquid were not, upon an accurate examination, 
identical with those of cinnamon water. Its odour, for ex- 
ample, was slightly different, and it reddened litmus, a cir- 
cumstance from which it may be inferred to contain cinnamic 
acid. It is therefore not unlikely that the oil may have ab- 
sorbed oxygen or have been otherwise altered during the 
distillation ; and as a confirmation of this opinion I may men- 
tion that the oil of cassia which is found in the market, is 
chiefly cinnamic acid, and that a cinnamon water prepared 
from it by a process directed in some of the pharmacopoeiae 
yields but a very minute proportion of the substance which 
is the subject of the present paper. 

With a view to the analysis of this compound the first 
point to determine was the proportion of iodide of potassium 
which it included. To accomplish this a known weight of it 
was heated in a small porcelain capsule, by which iodine and 
oil of cinnamon wei'e expelled in the vaporous state, and there 
remained amixtureof iodide of potassium with a little carbon 
resulting from the decomposition of a portion of the oil. The 
iodide of potassium was separated from the carbon by solu- 
tion in water, and the use of a single filter which had been 
previously deprived of all soluble matter by the action first 
of a dilute acid, and subsequently of distilled water. The 

12 



116 Dr.Apjohn on a new Compound of Iodide of Potassiumf 

filter being well washed, the solution was evaporated to dry- 
ness in a carefully counterpoised capsule, and then accurately 
weighed. The following are the results of three experiments 
thus conducted. 

IK IK 

(per cent.) 

3*37 grains gave 0*43 12'75 

8-00 1-03 12-87 

9-40 1-13 12-02 

The mean therefore of the numbers in the third column, 
or 12*55* is the quantity of iodide of potassium as obtained 
by me in 100 grains of the compound. 

The next step was to investigate the iodine associated not 
with the potassium but with the oil, and to effect this the fol- 
lowing was the course first pursued. 

A known weight of the compound was decomposed by a 
slight excess of an alcoholic solution of potash, and the whole 
was evaporated to dryness, by which the oil was partly vola- 
tilized and partly decomposed. Heat was now cautiously ap- 
plied, so as to reduce the iodate, which I have already stated 
to be always formed in such experiment, to the state of iodide 
of potassium, but not to volatilize any of the latter salt. The 
residue, first permitted to cool, was treated with distilled 
water, and passed through a filter to separate the carbon. 
The filter was well washed, and the solution, having been re- 
duced to a small bulk by evaporation, was precipitated by 
nitrate of silver, and the iodide of silver, first edulcorated 
three or four times with cold distilled water containing a few 
drops of ammonia, was finally dried, melted and weighed. 

In an experiment in which 10*33 grains of the compound 
were employed, the iodide of silver amounted to 7"-l'l grains, 
equivalent to 3'95 of iodine, or 38*24 for 100 grains of the 
compound. Now, if from this we subtract 9*58, the iodine in 
the 12*55 grains of iodide of potassium which we have already 
found to exist in 100 of the compound, we shall get for the 
per centage of iodine in union with the oil the number 28*66. 

Fearing that the heat applied in reducing the iodate of 
potash to iodide of potassium, might have either been insuffi- 
cient for the purpose or have volatilized some of the latter 
salt, I recommenced the estimation of the amount of free 
iodine, or rather of that united to the oil, by a somewhat dif- 
ferent process. 

A known weight of the substance was introduced into a 
test tube with water and zinc filings, and the other end being 

• This contains 9*58 grains of iodine. 



Iodine^ and the Essential Oil ofCinnamon» 117 

drawn out at the spirit lamp, it was hermetically sealed so as 
effectually to prevent the volatilization of iodine. Agitation 
was now resorted to, and a gentle heat at the same time ap- 
plied, which caused the separation of the oil, the iodine pre- 
viously combined with it having entered into union with the 
zinc and formed with it a salt dissolved by the water. The tube 
was now broken, and its contents having been thrown upon a 
single filter previously deprived of all soluble matter, distilled 
water was poured on until the entire quantity of the iodide of 
zinc was carried through. The washings were concentrated, 
suffered to cool, and then treated with the equivalent quantity 
of nitrate of silver, and the resulting precipitate (iodide of 
silver) having been, as in the previous experiment, sparingly 
washed with cold water containing a little ammonia, was dried 
and weighed. From this the total quantity of iodine in the 
compound, both that combined with the potassium and with 
the oil, was collected. But the quantity in the former state 
having been already ascertained, the difference is the quantity 
of iodine associated with the oil. 

In an experiment thus conducted 6'55 grains of the sub- 
stance yielded of iodide of silver 4«'52 grains, equivalent to 
37*20 grains of iodine for 100 of the compound. Subtracting 
from this 9'58, the iodine of the iodide of potassium, we ob- 
tain, as the representative of the amount of this element asso- 

28*66 + 27*62 

ciated with the oil, the number 27*62. Hence — 

2 

= 28*14 is the mean amount of the iodine in the latter state 

of combination as derivable from both experiments. But 

= 2*93, or 9*6 = 3. We thus arrive at the conclusion 

9*58 ' 

that for every atom of iodide of potassium in the substance 
under consideration there are three atoms of iodine in combi- 
nation with the oil of cinnamon. 

Before leaving this branch of the analysis, I may observe 
that the iodine of the oil may be directly obtained by decom- 
posing the compound in a glass tube at a red heat in contact 
with lime, and acting upon the residue with water which dis- 
solves the iodide of calcium, and along with it a little lime. 
The latter being separated in the usual manner by carbonic 
acid and boiling, the former may be precipitated by oxalate of 
ammonia, and the iodine estimated from the amount of carbo- 
nate of lime afforded by the oxalate when calcined at an ob- 
scure red heat. 

The experiment made upon this plan did not give a very 
satisfactory result; and, when I considered the great dispro- 



1 18 Dr. Apjohn om a new Compound of Iodide of Potassium, 

portion between the atomic weights of iodine and of lime I did 
not feel disposed to repeat the process. 

The iodine may also be taken out of the compound by filings 
of iron as well as those of zinc, in the form of iodide of the 
metal; and, though the theoretical objection just stated to the 
process by lime is equally applicable to this method, a single 
experiment, whose particulars I subjoin, thus conducted led 
to a conclusion corresponding very closely with that already 
obtained. 

8 grains of the compound gave 0*72 of peroxide of iron. 
But this amount of peroxide corresponds to 2'27 of iodine. 
Hence 

8 : 2'27 : : 100 : 28'41 - the 

percentage of iodine associated with the oil, and which ex- 
ceeds the result, 28*14, obtained by the other methods by a 
quantity so small that it may be viewed as affording a corro- 
boration of the correctness of the previous determination. 

Having determined the iodide of potassium and the iodine 
in union with the oil, we can now state the composition of the 
compound, assuming the residue to be oil of cinnamon. 

Iodide of potassium 12*55 

Iodine 28-14 

Oil of cinnamon 59*30 



99-99 

That it is the oil itself, and no oxidized or other modifica- 
tion of it, which exists in this compound, I have already as- 
signed reasons for believing ; and as, by the application of 
such heat as will fuse the compound, no water is set free, it 
becomes highly probable that the statement above made is a 
correct representation of its constitution. But the oil of cin- 
namon has been analysed, and through the researches of Du- 
mas we are acquainted with its real composition, which he has 
shown to be represented by the formula C^g Hg O^. If then 
the view numerically expressed above be the true one, the 
59*30 parts of oil must correspond to some integer or at least 
simple number of atoms. And, reciprocally, if we find such 
to be the case, we shall be fortified in the conclusion which 
we have drawn. 

With a view to this method of verification let the numbers 
which represent the iodide of potassium and iodine, and that 
which is supposed to represent the oil, be divided by their re- 
spective atomic weights, and let the quotients be reduced to 
others in the same ratio, nd so that the iodide of potassium 



Iodine, and the Essential Oil of Cinnamon. 119 

may be represented by unity. When these arithmetical ope- 
rations are performed we obtain the numbers in the second 
and third columns of the following table, the former being the 
quotients themselves, and the latter other numbers bearing to 
each other the same proportion. 

(1.) (2.) (3.) 

Iodide of potassium ... 12*55 0*075 I'OOO 

Iodine 28*14 0*223 2*973 

Oil of cinnamon 59*30 0*44.2 5*893 

The numbers, it will be seen, in the last column approxi- 
mate so closely to the integers 1, 3, and 6, as to leave little 
doubt that the true empirical formula is 
IK + Ia+Cing*, 
a conclusion which is strikingly confirmed by the following 
statement of the composition of our substance in 100 parts 
calculated upon this hypothesis. 

Iodide of potassium 12*26 

Iodine 28*08 

Oil of cinnamon 59*66 



100-00 
To apply, however, to this conclusion the most decisive 
test, it remained to burn the substance with oxide of copper, 
and see whether the carbonic acid and water thus obtained 
would correspond with the amount of oil of cinnamon ascribed 
to the compound. 

7*08 grains, Liebig's apparatus for potash being employed, 
yielded of carbonic acid 12*70 grains, and of water 2*60, 
equivalent to 3*513 carbon and 0*288 hydrogen. But, adopt- 
ing for a moment the empirical formula already arrived at, 
the 7'08 grains of the substance would contain 4*223 of oil of 
cinnamon. If, therefore, from this we deduct the carbon and 
hydrogen, we obtain the oxygen, and find the constituents of 
the oil to be as follows : 

Carbon 3*513 

Hydrogen 0*288 

Oxygen 0*420 

If these be divided by the atomic weights, and if also we sub- 
stitute for the quotients numbers in the same ratio with them, 
that for carbon being assumed 18, we obtain the following: 

Carbon 18*00 

Hydrogen 8*82 

Oxygen 1*60 

* Cin is assumed as the symbol for the oil of cinnamon. 



120 Dr. Apjohn on a new Compound of Iodide of Potassium. 

As the conjoint result, therefore, of our analysis and our hypo- 
thesis we find the formula for oil of cinnamon to be Cj^ Hg.ss 
Oj gg. Now this is so close to the formula of Dumas, viz. C^g Hg 
Og, particularly when we consider that owing to the fusibility 
of the compound, and the facility with which it is decomposed, 
heat could not be applied in drying the contents of the tube 
before the commencement of the combustion, and that conse- 
quently the hydrogen must have been too high and the oxygen 
too low, — considering this, I say, the accordance is so close 
as to leave no doubt that the empirical formula already given 
correctly represents the constitution of the compound submitted 
to analysis. It is scarcely necessary to say that the most pro- 
bable rational formula is that here subjoined: 
IK + 3(t + Cin2). 

From the analysis which I first performed, and of which I 
gave a brief account in the Chemical Section at the Liverpool 
Meeting of the British Association for the Advancement of 
Science, the formula deduced was 

IK + 2 (I2 + Cing), 

which differs from the preceding merely in containing one 
more atom of iodine. 

This compound appears interesting under many points of 
view. In the first place it is one of considerable complexity, 
is decomposed with an extreme facility, and is nevertheless 
perfectly definite in its composition, and even beautifully cry- 
stallized. 

In the second place it is a kind of double salt, composed of 
two haloid salts, in one of which the oil performs the very 
unusual function of an electro-positive or basic metal, — a cir- 
cumstance the more singular, as Dumas has shown that it 
unites also to the muriatic and nitric acids, forming with them 
binary compounds, the latter of which very readily crystal- 
lizes. The oil in fact thus appears to act the part of a metal 
as well as of an oxide. 

Lastly, I may observe that the method by which our com- 
pound was first accidentally formed, and is still best made, 
presents an instance of incompatibility which had not been pre- 
viously suspected, and will no doubt suggest to chemists ex- 
periments which will eventuate in the production of a series 
of similar substances. In reference, however, to this latter 
point I should add that Mr. Moore has applied to the other 
aromatic waters the very process which succeeds with cinna- 
mon water, but without obtaining a trace of any new product. 
It is possible, however, that new results might be obtained 
by substituting other metals for the potassium, and replacing 



Mr. T. Richardson upon the Composition of Coal. 121 

the iodine by bromine or even chlorine ; and I have indeed 
myself commenced some experiments with a view to this re- 
search. 



XVII. Researches upon the Composition of Coal. By Mr. 
Thomas Richardson.* 

[Illustrated by Plate III.] 

TylT'E are at present in possession of various analyses of coal, 
' ' but at the time when these were made the method of 
analysis was too imperfect to enable any chemist to obtain ac- 
curate results. This fact, with the great and important use 
made of coal in manufactures, induced me to undertake the 
present researches. They have been conducted with every 
possible care and attention, and throughout I have been in- 
debted to the kind instruction and advice of Professor Liebig. 
In the first part of the present memoir the various methods 
employed in determining the different constituents will be 
shortly described ; and in the second part, the analyses of the 
various coals, &c. 

I. METHODS EMPLOYED IN DETERMINING THE DIFFERENT 
CONSTITUENTS. 

Hygrometric Moisture, S^c. 

The first object was to determine the amount of water which 
the coal contained, and whether this water was chemically 
combined, or merely hygrometrical. With this view the fol- 
lowing experiments were made : 

1 . A certain quantity of coal, finely powdered, was dried at 
100° C by means of Professor Liebig's apparatus, and the loss 
amounted to r23 per cent. 2. -SS-i grm.f coal, as finely 
pounded as the preceding, was dried in a chloride of zinc bath 
at the temperature of 185° C when it sustained a loss of '0105 
or 1*229 per cent. 

It may, therefore, be concluded that if coal contains water, 
it must exist in a state of the most intimate chemical combi- 
nation. 

Ashes. 

The determination of the ashes was very simple. A weighed 
quantity of coal was heated to redness in a small platina cru- 
cible, till the whole of the carbon was oxidized, and the resi- 
due constituted the amount of ashes contained in the specimen. 

• From the Transactions of the Natural History Society of Newcastle- 
upon-Tyne, vol. ii. p. 401. 

t The measure of quantity used in these analyses is the French gramme ; 
1 gramme French = 15*433 grains English. 



122 Mr. T. Richardson's Researchet 

These ashes, treated with muriatic acid, afforded not the 
slightest perceptible trace of carbonic acid. When they were 
boiled with carbonate of soda, the clear filtered solution of 
the same, saturated by nitric acid, produced not the smallest 
milkiness with a salt of barytes. 

Carbon and Hydrogen. 

The estimation of the carbon and hydrogen was partially 
made by means of oxide of copper, but generally with melted 
chromate of lead. The apparatus was perfectly the same as 
that employed by Professor Liebig, the only difference being 
in the use of the above salt. A more exact account of the 
employment of this substance will be found in another me- 
moir. 

Azote. 

With respect to the method employed in the determination 
of the azote, it will be necessary to enter more minutely into 
particulars (though perhaps a digression from the proper sub- 
ject of the present memoir,) to show that no exertions on my 
part have been wanting to obtain an exact result. Five or six 
analyses were made with the apparatus which Professor Lie- 
big has already described for the absolute estimation of azote. 
The azote in all the analyses amounted to nearly 4 per cent. 
When it is remembered what a small quantity of sal ammo- 
niac is obtained in every gas manufactory, this amount will at 
once appear much too great. 

The method of determining the azote by means of its rela- 
tion to the carbonic acid was then resorted to, but it was 
found impossible to measure the volume of the azote. I could 
only in this way guess at the true quantity of azote, and it 
appeared to be as 1 H : 100 COg. 

At the suggestion of Professor Liebig, the following plan 
was then pursued : — The apparatus, as per diagram, (Plate 
in.) consisted of an ordinary tube of combustion a, about 20 
inches long, and from '4 to '5 inch diameter, connected with 
a tube b, having 2 balls, and about 10 inches long and '4 inch 
in diameter. A small thermometer tube c was united to the 
other part of the apparatus by means of a piece of caoutchouc, 
and conducted the gas into a receiver d, which was partially 
filled with mercury. A part of the tube c remained always 
above the level of the mercury in the receiver d. 

The tube of combustion a contained in the hermetically 
sealed end from 2 to 2^ inches of hydrate of lime, then one 
inch oxide of copper, afterwards the mixture of the substance 



land, ^Ji'dm^ r/uL ,i/a^. VoL J2/1. 2Z2II 





%L 



*' i' ^ 



C r f^iK. 



IBP' 



upon the Composition of Coal. 123 

with oxide of copper, washings* of the same, a further quan- 
tity of oxide of copper, and lastly slips of metallic copper. 
The shaded part of the tube b was filled with hydrate of 
potash. 

The whole apparatus being arranged, the receiver d was 
raised a little, and if the mercury retained its new level, the 
apparatus was considered air-tight. The air in the receiver d 
was now measured, the temperature and barometer being noted 
at the same. The combustion was conducted in the usual 
way, the water and carbonic acid were absorbed by the pot- 
ash, while the azote forced the receiver to rise. When the 
combustion was finished, the hydrate of lime was heated slowly 
to redness, and the aqueous vapour thus formed drove out all 
carbonic acid into the tube of absorption. The apparatus was 
now allowed to cool, while the aqueous vapour condensed, and 
the increase of volume in the receiver denoted the quantity of 
azote in the substance submitted to analysis. 

The precautions necessary to be taken are the following : — 
The mixture of the substance with the oxide of copper must 
be most intimately made, and the combustion proceeded with 
as slowly as possible; the pressure of the gas in the receiver 
must also be quite equable, otherwise the tube of combustion 
will be either increased or diminished in size, and consequently 
an incorrect result obtained ; the heating of the hydrate of lime 
must be gradually performed ; and care must be taken on the 
cooling of the apparatus that the condensed vapour which 
flows back be retained in the first ball of the tube of absorp- 
tion, which is blown for this purpose. 

By this method the following results were obtained : 

•2768 grm. Uric acid were submitted to analysis. 

27°5 Barometer at the time of the experiment. 

12° Thermometer at the time of the experiment. 

^G'O cc ... Air in the receiver before commencement. 
120*0 cc ... Mixture of gas and air after cooling. 



76*0 cc ... Azote. 

76 cc azote reduced to 0° thermometer, and 28° barometer, 
give 70*4 cc which is equal to 32'24 per cent. From the ana- 
lysis of Liebig, this acid contains 33*36 per cent., so that there 
is a loss of 1*12 per cent. 

The analysis was repeated, but the loss was nearly the 
same. 

* By washings I mean the oxide of copper employed in cleaning out the 
mortar wherein the mixture of the substance has been made. 



124< Mr. T. Richardson's Researches 

•3244 grm. Anhydrous amygdalme were submitted to analysis. 

27°7 Barometer at the time of experiment. 

12°6 Thermometer at the time of experiment. 

15*0 cc ... Air before commencement. 
20°5 cc ... Gas and air after cooling. 

5*5 cc ... Azote. 

5'5 cc Azote reduced to 0° thermometer and 28° barometer 
give 5*19 cc, equivalent to 2*0 3 per cent., which is, according 
to Liebig, 1 per cent, less than the true quantity. 

From these experiments there appears to be a constant error 
of 1 per cent. This error was supposed at first to arise from 
a diminution of the oxygen in the air of the tube of combus- 
tion, destroyed in oxidizing the carbon and hydrogen. With 
the view to obviate this cause of failure, carbonate of copper 
was mixed with the oxide of copper, so that before the com- 
mencement of the decomposition of the organic body, the 
heat expelled the carbonic acid of the CO^, Cu O, and drove 
out all air in the tube of combustion. 

With this modification — 

•3566 grm. Amygdaline were submitted to analysis. 

27°6 Barometer. 

11°4 Thermometer. 

14 cc ... Air in the receiver before commencing. 
on /.^ fGas and air at the close of the experiment after 
(^ cooling. 



6 cc ... Azote. 
6 cc Azote reduced to 0° thermometer and 28° barometer give 
5'65cc which equals 2*01 per cent. The loss here amounts 
again to 1 per cent. 

•2456 grm. Crystallized asparagin. 
27°4 ... Barometer. 
12°7 ... Thermometer. 

43 cc ... Air at the commencement in the receiver. 

81 cc ... Air and gas when finished. 



38 cc ... Azote. 
38 cc Azote reduced to 0° thermometer and 28° barometer give 
35*49 cc which equals 18*32 per cent. The loss here amounts 
to '64 per cent. 

Oxide of copper having the property of absorbing carbonic 
acid from the air, which is expelled by the heat in the tube of 
combustion, and its place occupied by the mixture of azote 
and air in the end of the experiment, it was supposed that 



upon the Composition of Coal. 125 

this might be the cause of the error. Bichromate of potash 
and dichromate of lead were then successively employed in- 
stead of oxide of copper, but it was found impossible to avoid 
the formation of deutoxide of azote with these substances, in 
such quantities as to be reduced by the copper. Oxide of 
lead was also used, but the combustion was quite imperfect, 
and the quantity of ammonia formed, very great. Oxide of 
copper strongly heated, was at last employed, but the error 
remained the same. 

The method remains thus at the present time, but I hope, 
by further investigation, to discover the cause of the error*. 
The error being thus confined to 1 per cent., two analyses of 
coal were made, in order to obtain some idea respecting the 
amount of the azote. These coals will afterwards be more 
minutely described. 

I. '283 grm. Coal from the neighbourhood of Edinburgh. 

27°7 Barometer. 

is"* Thermometer. 

11'8 cc ... Air in the receiver. 

12'7 cc ... Gas and air after the experiment. 



•9 cc ... Azote. 
•9 cc Azote reduced to 0° thermometer and 28° barometer give 
•84? cc which equals '38 per cent. 

II. '300 grm. Coal from Garesfield near Newcastle-on- 
Tyne, produced no gas, but there appeared to be a diminu- 
tion of '30 cc. 

From the above experiments it clearly appears, that the 
coal cannot contain more than 2 per cent, of azote, but with 
the present means of analysis at our disposal it is impossible 
to determine the true amount. 

II. ANALYSES OF THE COALS, &C. 

The arrangement of the various coals, proposed by Dr. 
Thomson, has been for the present adopted in the following 
account. Two specimens of each of these varieties from dif- 
ferent localities have been analysed. There are four varieties, 
viz.. Splint, Cannel, Cherry, and Caking. 

I. VARIETY — SPLINT COAL. 

1. Specimen from Wylam Banks. 
This coal is not at present worked ; it is a thin bed very 
low down in the Newcastle coal series, and appears in this spot 

* Since the above was first printed, it has occurred to me that the error 
arises from the absorption of the oxygen gas of the air in the apparatus, 
by the reduced oxide of copper, after the analysis is finished and during the 
cooling of the tube of combustion. 



126 Mr. T. Richardson's Researches 

by the river Tyne cutting through it. Colour black ; lustre 
glimmering; difficultly frangible; principal fracture imperfect 
conchoidal; ciross fracture uneven and splintery; specific gra- 
vity 1-302. 

The determination of the ashes, as already described, was 

I. r234-grm. coal left as residue 'ITlSgrm. 

II. •OSG'igrm '0122 grm. 

1-3204 -1837 

which amounts to 13-912 per cent. 

Burnt in the usual way with oxide of copper : 
I. -270 grm. coal gave -732 grm. COg and -1 52 grm. Hg O 

II. -252 grm -678 grm. COg and -1385 grm. Hg O 

Burnt v/ith chromnt^-of lead in the manner to be described: 

III. •3414-grm. coal gave -927gnn.C02and •1922grm.H20 

IV. •3955grm l-0703grm.CO2and-2i76grm.H2O 

These results give in 100 parts : 

I. II. III. IV. 

Carbon 74-961 74*381 75-071 74-878 

Hydrogen 6-254 6-111 6*243 6-114 

Azote and oxygen 4-873 5-596 4-774 5*096 

Ashes 13-912 13-912 13*912 13*912 



100*000 100*000 100-000 100*000 



The relation of the carbon and hydrogen is clearly as 1 : 1. 

2. Specimen from Glasgow. 
The splint coal occurs associated with cherry coal in the 
Glasgow coal field. The fifth bed is almost entirely consti- 
tuted of this species. It is very highly esteemed for manu- 
facturing and household purposes. Colour is black, with a 
little brown ; lustre glimmering ; difficultly frangible ; frac- 
ture uneven and splintery ; specific gravity 1*307. 
Ashes determined in the usual way gave — 

I. -214 grm. coal left as residue '0024 grm. 
II. -238 grm -0027 grm. 

•452 -0051 

which amounts to 1*128 per cent. 

Burnt with chromate of lead as usual — 
I. •2798grm. coal gave •838grm. CO2 and -1401 grm. HgO 

II. -2596 grm -7818grm. COsand *1272grm. H2O 

III. •2378grm -7115grm. COgand -U71grm. HgO 

which yields in 100 parts. 



upo7i the Composition of Coal. 1 27 

I. II. III. 

Carbon 82-813 83-230 82-730 

Hydrogen 5-562 5-4<42 5-469 

Azote and oxygen 10-497 10-200 10-673 

Ashes 1-128 1-128 1-128 



100-000 100-000 100-000 

The relation of the carbon to the hydrogen in this speci- 
men is as 1-231 : I'OOO or 5 : 4. 

II. VARIETY. — CANNEL COAL. 

1. Specimen from, Lancashire. 

The locality of this specimen is Wigan, where it has for a 
long time been worked. From its capability of receiving a 
fine polish, it is made into toys, &c. 

Its colour is greyish black ; the lustre is highly glistening ; 
fracture is large conchoidal. It is not so hard as the splint 
coal and is sectile. Specific gravity 1-319. 

The ashes determined in the usual way were: 

I. -1706 grm. coal left as residue... -0043 grm. 
II. •1825grm -0047 grm. 

•3531 -0090 

which amounts to 2-548 per cent. 

Burnt with chromate of lead in the usual way : 
I. -2937 grm. coal gave -890 grm. COo 

II. -3178 grm -962 grm. COg and -1624 grm. HgO 

III. -2819 grm -8545 grm. CO2 and -1432 grm. HgO 

or in 100 parts 

I. II. III. 

Carbon 83-789 ... 83-698 ... 83-808 

Hydrogen 5-677 ... 5*643 

Azote and oxygen 8-077 ... 8-001 

Ashes 2-548 ... 2-548 ... 2-548 

100-000 100-000 

The relation of the carbon to the hydrogen is in this coal as 
1-207 : 1-000 or 6 : 5. 

2. Specimen from Edinburgh. 

This coal is called in Scotland Parrot coal^ because its 
particles, when heated, fly off from one another with a crack- 
hng noise. It occurs in many of the series in the Edinburgh 
coal field. It splits easily, and throughout its substance se- 



128 Mr. T. Richardson's Researches 

veral well-defined impressions of S^z^vwana^co/rf^s are found. 
Colour is black with gray ; lustre approaches that of glisten- 
ing; fracture, imperfect conchoidal; sectile and frangible; 
specific gravity, 1*318. 

The determination of the ashes was as follows : 

I. '2007 grm. coal left as residue '0295 grm. 

II. 'ISSSgrm -0268 grm. 

•3865 -0563 

This amounts to 14<'566 per cent. 
Burnt with chromate of lead: 
I. -3022 grm. coal gave -737 grm. CO2 and •1468 grm. HgO 
II. •294. grm. •7205grm.CO2 and -1434 grm. H2O 

Expressed in 100 parts. I. II. 

Carbon 67*434 ... 67*760 

Hydrogen 5^394 ... 5*416 

Azote and oxygen 12*606 ... 12-258 

Ashes 14*566 ... 14*566 



100*000 100*000 

The relation of the carbon to the hydrogen is in this speci- 
men as 1*020 : 1000 or 1 : 1. This differs from the cannel 
coal from Lancashire, but agrees with the splint coal of Wy- 
1am Banks, near Newcastle. Between the splint and cannel 
coals there is at all times much similarity, and this is counte- 
nanced again by the above results. 

III. VARIETY. — CHERRY COAL. 

1. Speci7nenfrom Jarrow, near Newcastle. 

This species of coal occurs more or less in every coal field, 
often forming thin beds or layers in the midst of other coals. 
The specimen submitted to analysis was obtained from a thin 
seam passed through while sinking the shaft of the mine 
deeper. Colour, beautiful jet black ; lustre, resinous, splen- 
dent; principal fracture, straight, uneven; cross fracture, 
conchoidal; not very hard and easily frangible; specific 
gravity, 1*266. 

The determination of the ashes was as follows : 

I. *2567 grm. coal left as residue '0045 grm. 
II. -3457 grm *0056 grm. 

•6024 '0101 

amounting to 1 *676 per cent. 
Burnt with chromate of lead. 



upon the Composition of Coal, 129 

I. •4164' grm. coal gave 1*2755 grm.CO^and'lSQBgrm.HgO 

II. -SlUgrm •9573grm. COaand-UUgrm. HgO 

expressed in 1 00 parts : 

I. II. 

Carbon 84.-691j ... 84-998 

Hydrogen 5-054 ... 5-043 

Azote and oxygen 8*576 ... 8-283 

Ashes 1-676 ... 1-676 



100-000 100-000 

The relation of the carbon to the hydrogen in this specimen 
is as 1-370 : 1-000 or 4*110 : 3*000. 

2. Specimen Jrom Glasgow. 

The greater portion of the coal obtained from Glasgow 
consists of this species; it constitutes the chief part of the 
four uppermost beds. 

Colour, jet black ; lustre, not so splendent as that of Jarrow. 
In its other characters it is quite the same as the preceding 
specimen. Specific gravity 1-268. 

The determination of the ashes was as follows : 

I. -2410 grm. coal left as residue -0035 grm. 
II. •1810grm -0025 grm. 

*4220 *0060 

which is equal to 1*421 per cent. 

Burnt with chromate of lead: 

I. *278 grm. coal gave -8148 grm. CO^ and -1379 grm. HgO 

II. -308 grm -9073 grm. CO^ and -1494 grm. HgO 

III. -2721 grm -7983 grm. CO^ and -1338 grm. HgO 

which produces in iOO parts : 

I. II. III. 

Carbon 81-041 ... 81-450 ... 81*121 

Hydrogen 5*509 ... 5*387 ... 5*461 

Azote and oxygen 12*029 ... 11-742 ... 11-997 

Ashes 1*421 ... 1*421 ... 1*421 



100-000 100-000 100-000 

The relation of the carbon to the hydrogen in this coal is as 
1-216 : 1-000 or 6 : 5. This relation differs from that of the 
preceding specimen of this species. 

IV. VARIETY — CAKING COAL. 

1. Specimen from Garesfield, near Newcastle. 

This specimen was obtained from one of the lowest seams 
Phil, Mag. S. 3. Vol. 13. No. 80. Aug. 1838. K 



130 Mr. T. Richardson's Researches 

in the Newcastle coal field. This coal is of a rich bituminous 
nature, caking or melting when heated ; it is from this pro- 
perty that it receives its name. 

Colour, black; lustre, shining, resinous ; principal fracture, 
straight ; cross fracture, uneven and cross-grained ; the frag- 
ments have more or less a cubical shape ; soft and very easily 
frangible ; sectile. Specific gravity 1 '280. 

The estimation of the ashes was as follows : 

I. '2080 grm. coal left as residue '0039 grm. 

II. -2800 grm -0029 grm. 

•4880 -0068 

which amounts to 1*393 per cent. 
Burnt with chromate of lead : 
I. '2977 grm. coal gave •9454- grm. COg and '1383 grm. H^O 

II. -3149 grm 1-0035 grm. COg and '1509 grm. H2 O 

or in 100 parts : 

I. II. 

Carbon 87*809 ... 88*095 

Hydrogen , 5-159 ... 5*320 

Azote and oxygen 5*639 ... 5-192 

Ashes 1-393 ... 1*393 



100*000 100*000. 



The relation between the carbon and hydrogen in this speci- 
men is as 1-377 : 1*000 or 4 : 3. 

2. Specimen from South Hetton. 

This coal occurs in the county of Durham, and is worked 
through the magnesian limestone. It is regarded as one of 
the best coals. Its characters perfectly correspond with 
those of the preceding specimens. Specific gravity r2'74. 

The ashes determined in the usual way were as follows : 

I. -2400 grm. coal left as residue ... -0060 grm. 
II. -2604 grm *0066 grm. 

•5004 -0126 

which amounts to 2-519 per cent. 
Burnt with chromate of lead : 
I. -2929 grm. coal gave *8855grra. CO<^ and -1358 grm.H^O 

II. -2705 grm •8116grm.C02and-1265 grm.HgO 

expressed in 100 parts: 



upon the Composition of Coal. 

I. II. 

Carbon 83-588 ... 82*960 

Hydrogen 5-150 ... 5-193 

Azote and oxygen 8-743 ... 9*328 

Ashes 2-519 ... 2-519 



100-000 



100-000 



131 



The relation in this specimen is the same as in the former, 
viz., 1-315C : 1-OOOH or 4 : 3. 

For the sake of convenience and comparison, the following 
table contains the mean of the various analyses of each speci- 
men. 

TABLE I. 



Species of Coal, 


Locality. 


Carbon. 


Hydrogen. 


Azote and 
Oxygen. 


Ashes. 


Splint 

Cannel 

Cherry 

Caking 


Wylam 

Glasgow 

Lancashire ... 
Edinburgh ... 
Newcastle ... 

Glasgow 

Newcastle ... 
Durham 


74-823 
82-924 
83-753 
67-597 
84-846 
81-204 
87-952 
83-274 


6-180 
5-491 
5-660 
5-405 
5-048 
5-452 
5-239 
5-171 


5-085 
10-457 

8-039 
12-432 

8-430 
11-923 

6-416 

9-036 


13-912 
1-128 
2-548 

14-566 
1-676 
1-421 
1-393 
2-519 



TABLE II. 







Quantity of Oxygen 


Relative quantity 


Relative quantity 






necessary to the perfect 


of heat given out 


of heat given out 


Secies of 


Locality. 


combustion of 100 parts 


by the same weight 


by the samevo. 


Coal. 




of coal, subtracting the 


of coal. 


lume of coal. 






Oxygen contained in 


Edinbro'= 100-00. 


Edinbro' = 100-00. 






the coal. 






Splint 


Wylam... 


240-1 


110-34 


108-99 




Glasgow 


250 5 


115-12 


114-15 


Cannel 


Lancashire 


256-4 


117-83 


11 7-91 




Edinburgh 
Newcastle 


217-6 


10000 


100-00 


Cherry 


253-9 


116-68 


112-07 




Glasgow 


244-0 


112-12 


107-78 


Caking 


Newcastle 


266-7 


122-56 


119-03 




Durham... 


250-2 


114-98 


111-31 



The first table requires no explanation. The second table 
contains in the first column, that quantity of oxygen which 100 
parts of the different coals abstract from the air for perfect 
combustion. This quantity of oxygen expresses the relative 
heating power of the different coals, in admitting that the 
quantity of heat evolved by a combustible substance is pro- 
portional to the quantity of oxygen which is consumed in its 

K2 



132 Mr. J. J. Griffin's Arithmetical Analysis of 

perfect combustion. This relation, according to weight and 
volume, is given in the second and third columns. 

For example, 100 volumes being taken, the Lancashire 
coal gives out more heat than the same volume of Edinburgh 
coal by a quantity expressed by 17'91 : and 100 parts by 
weight being taken, the former coal surpasses the latter in 
the heat evolved by the quantity expressed by 17'83. 

XVIII. Arithmetical Analysis of mixed Salts of Potassium and 
Sodium. By John Joseph Griffin, Author qf^^ Chemical 
Recreations."* 

Analysis of Chlorides. 

METHOD. 

a. 'liyEIGH the chlorides. 

1). ^^ Dissolve the chlorides, precipitate with nitrate of 
silver, and weigh the chloride of silver. 

c. Multiply the weight of the mixed alkaline chlorides a, 

by 1-92404.. 

d. Subtract the product of the multiplication c, from the 

weight of the chloride of silver h. 
c. Divide the residue of the subtraction rf, by 0*52201. 

f. The product of the division ^, is the weight of the chloride 

of sodium contained in the mixture a. 

g. The dilFerence between the weight of the mixed chlorides 

a, and that of the chloride of sodium^ is the weight of 
the chloride of potassium. 
Explanation. — The quantity of chloride of silver producible 
by chloride of sodium above the quantity producible by chlo- 
ride of potassium, is 0*52201 for every unit of the given chlo- 
ride of sodium. For, 

1 of chloride of sodium produces of chloride \ 2-44605 

of silver J 

1 of chloride of potassium produces of chlo-\ 1.92404 
ride of silver J 

The excess being = 0*52201 

Consequently, in any quantity of chloride of silver pro- 
duced by a mixture of chloride of sodium and chloride of 
potassium, we have 

First, as much chloride of silver as is producible by a quan- 
tity of chloride of potassium of equal weight to the given 
mixture of chlorides ; and 

Secondly, as much more chloride of silver as is equal to 

* Communicated by the Author : a paper on indirect chemical analysis, 
by Dr. G. Bird, will be found in vol. xii. p. 229. 



mixed Salts of Potassium and Sodium. 133 

the quantity producible by chloride of sodium above the 
quantity producible by chloride of potassium ; this additional 
quantity of chloride of silver being equal to 0*52201 multi- 
plied by every unit of chloride of sodium present in the 
mixture. 

Wherefore, 

In Operation c, we multiply the mixed chlorides by r9240'l' 
to find the quantity of chloride of silver producible by the 
given weight of chloride of potassium alone. 

In Operation d, we subtract this quantity from that of the 
chloride of silver actually produced in experiment b, by the 
mixed alkaline chlorides ; and thus determine the amount of 
the excess produced by the chloride of sodium. 

In Operation e, we divide this excess by 0*52201 to ascer- 
tain the number of units, or the weight, of the chloride of 
sodium contained in the mixture. 

Tables of Data. — 1. To find the weight of the components 
and equivalents of any quantity of chloride of sodium, multi- 
ply it, 

by 0*39656 for the sodium it contains. 
0*60344? for the chlorine. 
0*53289 for its equivalent of soda. 
And by 2*44'605 for the quantity of chloride of silver which 
it produces by precipitation. 

2. To find the weight of the components and equivalents 
of any quantity of chloride of potassium, multiply it 
by 0*52534- for the potassium it contains. 

0*47466 for the chlorine. 

0*63257 for its equivalent of potash. 

And by 1*92404 for the quantity of chloride of silver which 
it produces by precipitation. 

These tables explain the reason why a greater quantity of 
chloride of silver is produced by chloride of sodium than by 
chloride of potassium. The reason is that chloride of sodium 
contains 60 per cent, of chlorine, while chloride of potassium 
contains little beyond 47 per cent. I point out this fact, be- 
cause it shows the sort of differences upon which all indirect 
analyses must be founded. 

Example. — In the analysis of a mineral that contains both 
potassium and sodium we have proceeded so far as to have 
nothing to separate but these two metals, which are present 
in the condition of chlorides. 

a. The mixture of chlorides weighs 5 grains. 

b. It produces by precipitation 11*18623 grains of chloride 

of silver. 



13^ Analysis of mixed Salts of Potassium and Sodium, 

c. The weight of the mixture a, 5 grains, multiplied by 

1 •92-^04. gives 9-62020. 

d. 9-62020 subtracted from 11-18623 gives 1-56603. 

e. 1-56603 divided by 0*52201 gives 3. 

f. The weight of the chloride of sodium in the mixture a is 

3 grains. 

g. The weight of the chloride of potassium is 2 grains. 
The quantity of sodium equivalent to the chloride of so- 
dium is 3 X 0-39656 

The quantity of soda is 3 x 0-53289 

The quantity of potassium equivalent to the chloride of 

potassium is 2 x 0-52534< 

The quantity of potash is 2 x 0*63257 

Analysis of Sulphates. 

METHOD. 

a. Weigh the mixed sulphates. 

h. Dissolve the sulphates, precipitate with chloride of barium, 
and weigh the sulphate of barytes. 

c. Multiply the weight of the mixed alkaline sulphates a, by 

1*33633. 

d. Subtract the product of the multiplication c from the 

weight of the sulphate of barytes b. 

e. Divide the residue of the subtraction d by 0*29814. 

f. The product of the division e is the weight of the sulphate 

of soda contained in the mixture a. 

g. The difference between the weight of the mixed sulphates 

a, and that of the sulphate of soda^ is the weight of the 

sulphate of potash. 
Explanation. — The quantity of sulphate of barytes pro- 
ducible by sulphate of soda above the quantity producible by 
sulphate of potash, is 0*29814 for every unit of the given sul- 
phate of soda. For 

1 of sulphate of soda produces of sulphate of barytes 1*63447 
1 of sulphate of potash produces of sulphate of barytes 1*33633 

The excess being = 0*29814 
The further explanation of this method is the same as the 
explanation of the analysis of the alkaline chlorides. 

Tables of Data. 

1. To find the weight of the components and equivalents 
of any quantity of sulphate of soda, multiply it by 
0*326095 for the sodium it contains. 
0-673905 for the sulphur and oxygen. 
0-43819 for the soda. 
0-56181 for the sulphuric acid. 



Mr. C. Binks o?t Electricity, 135 

And by 1'6344<7 for the quantity of sulphate of barytes 
which it produces by precipitation. 
2. To find the weight of the components and equivalents 
of any quantity of sulphate of potash, multiply it 
by 0'449019 for the potassium it contains. 

0*550981 for the sulphur and oxygen. 
0-54067 for the potash. 
0*45933 for the sulphuric acid. 
And by 1*33633 for the quantity of sulphate of barytes 
which it produces by precipitation. 
Example. — In the analysis of a sample of commercial alum, 
we have proceeded so far as to have nothing to separate but 
sulphate of potash from sulphate of soda, both of which 
alkalies have been detected by previous testing. 

a. The mixture of sulphates weighs 7 grains. 

b. It produces by precipitation 10*54687 grains of sulphate 

of barytes. 

c. The weight of the mixture a, 7 grains, multiplied by 

1*33633 gives 9*35431. 

d. 9*35431 subtracted from 10*54687 gives 1*19256. 

e. 1*19256 divided by 0*29814 gives 4. 

f. The weight of the sulphate of soda in the mixture a is 4 

grains. 

g. The weight of the sulphate of potash is 3 grains. 

The quantity of sodium equivalent to the sulphate of soda, 
is 4x0*326095 

The equivalent of soda, is j • • • 4x0*43819 

The quantity of potassium equivalent to the sulphate of 
potash, is 3x0*449019 

The equivalent of potash, is 3 x 0*54067 

The atomic weights employed in these calculations are 
those of Berzelius. 
Glasgow, March 19, 1838. 

XIX. On some of the Phcenomena andLaws of Action of Voltaic 
Electricity, and on the Construction of Voltaic Batteries, 
Sfc. By Christopher Binks. A second Communication, 
addressed to J. F. Daniell, Esq. F.R.S., Sfc, Professor of 
Chemistry in King^s College, London. Part the Second. 

[Continued from Part i. p. 75.] 

Section IV. 
73. nPHE ultimate object of the following experiments is to 
-*■ determine on the most advantageous construction of 
the voltaic battery ; that is, such a construction as shall com- 



136 



Mr. C. Binks on Electricity, 



mand its greatest effects, of any kind, with the least expendi- 
ture of materials. 

The process by which this ^nd is attempted to be reached, 
is by first determining the laws of action affecting the opera- 
tions of single arrangements ; and afterwards, when this is 
completed, extending the examination into the phaenomena of 
compound ones. 

74. These examinations are, in the first instance, restricted 
to the phaenomena of arrangements in which sulphuric acid, 
diluted, is employed as the exciting agent. It is then sought 
to determine, by extending the inquiry into the less familiar 
operations of other kinds of arrangement, such, for example, 
as include the sulphate of copper as an element, whether the 
same results can be obtained under these as under the former 
conditions, or in what respects they differ ; the chief object 
through all being the application of the principles, thus sought 
to be established, to the construction of the battery. 

To determine the comparative amount of voltaic action in- 
duced in any single arrangement by acid solutions of different 
degrees of strength. 

75. The plates of the voltaic couple here used were of an 
equal size, each presenting an entire surface of four square 
inches to the action of the acid mixture ; they were separated 
from one another by a distance of half an inch : this, as well 
as every other attendant condition, being, of course, main- 
tained exactly alike in every trial. The acid mixture was 
composed, in the first instance, of one part by measure of 
common sulphuric acid, and 100 parts of water; and after- 
wards of larger proportions of acid, as shown in the sub- 
joined table, in which the column of densities represents the 
actual strength of the mixture with the greater nicety. The 
amount of action in each case is estimated by the weight of 
zinc lost in a given equal time. 

76. Table of the effects of acid mixtures of different de- 
grees of strength. (No. 4.) 



Parts by measure of 

Sulph. aeid in 100 

of water. 


Specific gravity of 

the mixtures at 

Temp. 65° Fahr. 


Quantity of Zinc in 
grains lost in a given 
time, or 10 minutes. 


Effects compared 

with the first 

Result. 


1 


1-013 


1-6 


= 1 


3 


1-034 


2-6 


= 1-6 


6 


1-063 


31 


= 1-9 


9 


1-090 


3-9 


= 2-4 


12 


M17 


4-8 


= 4-0 


15 


M37 


5-1 


= 4-4 


18 


1-164 


4-7 


= 2-9 


21 


1190 


4-5 


== 2-8 


24 


1-213 


3-9 


= 2-4 



Voltaic Batteries^ 8^c. 137 

77. The comparative effects of these different acid solutions 
were then sought for under two distinct modifications of the 
experiments as just stated : first, when the elementary plates 
of the couple used were of a different size from those by which 
the results in the above table had been obtained ; and secondly, 
when the two plates of the couple were placed at a different 
distance from one another than that stated above ; but whilst 
every other attendant circumstance, in either case, was main- 
tained precisely the same as at first. 

78. For the former purpose a smaller couple was taken 
and immersed in the different acid mixtures successively, as 
before ; when the weight of zinc lost, in the same time, was 
of course less in the aggregate than when the larger couple 
was employed ; but the difference between the amount of loss 
occasioned by the different acid mixtures was precisely after 
the same rate as had been previously determined for thejother 
couple, and as that rate is stated in the fourth column of the 
above table. 

79. And when a couple was employed of the same size as 
the first (75.), but with its plates placed at a greater distance 
from one another than in either of the previous instances, in 
like manner to the last, the action in the aggregate was re- 
duced by reason of the greater distance, but the comparative 
rate at which each acid mixture acted upon this couple was 
precisely the same as had already been found in the two pre- 
vious instances. 

80. It appears, therefore, that the comparative effects of 
these different acid solutions are the same whatever may be 
the size of the voltaic couple, or whatever may be the distance 
between its elementary plates ; and the above table, therefore, 
represents the comparative rate in which dilute sulphuric 
acid of different degrees of strength acts upon any voltaic 
arrangement. 

81. A review of this table shows, 1st, that the greatest 
amount of action induced in any arrangement by dilute sul- 
phuric acid takes place when the mixture is in the proportion 
of about 15 parts by measure of ordinary acid, and 100 of 
water; or of the average specific gravity of 1*140: 2ndly, 
that the rate of increase of action is neither the same as the 
rate of increased proportions of the acid, nor of the specific 
gravity of the mixture, but occurs in some other simple rate, 
bearing however no very obvious relation to any apparent at- 
tendant circumstances. 

82. The acid mixtures which will subsequently be employed 
in these experiments are the first four of the above table. 



138 Mr. C. Binks on Electricity, 

Section V. 
To determine the comparative amount of action in any 
single voltaic arrangement when its plates are placed at dif- 
ferent distances from one another. 

83. The two plates of a voltaic couple may be either of an 
equal size, or unequal, and the difference in size which may 
exist between the two is unlimited. 

The couple itself, considered as a couple, may either be 
large or small also, to an unlimited extent. 

The distance between the two plates of any couple, what- 
ever its size, or whatever the relative proportions of the plates, 
may also be varied without limitation. 

The acid mixtures also, in which any voltaic couple is made 
to operate, may be of any required degree of strength. 

84. The immediate object in hand is to determine the ef- 
fects of distance; but these must be sought for under every 
possible condition of the arrangements as regards the size of 
the couple used, the relative proportions of its plates, and 
the strength of the exciting acid. 

To determine the law of distance when the two elementary 
plates are of an equal size. 

85. (a). A voltaic couple having on each plate an entire 
surface of 6 square inches, had its plates placed successively 
at the distance from one another of \ of an inch, 4 inches, 
and 24, and the quantity of hydrogen by measure, yielded in a 
given time at each of these positions, was respectively equal to 

OA ea A cr. f lU 50ths of a 

84. 58 and 39 < , • • i 
L cubic mch. 

86. {b). Another couple, exactly one half the size of the 
last, yielded under precisely the same conditions the respect- 
ive measures of 

An oi I oi rin50thsofa 
46. 31 and 21 < u • • u 
L cubic men. 

87. {c.) Another couple, one fourth the size of the first 

one, and placed under the same circumstances, yielded the 

numbers 

r,r. ,c, J lo r in like measures of 
26. 18 and 12 < , , . ,, 

1^ hydrogen m the same time. 

88. These experiments determine that whatever may be 
the size of the couple itself, its elementary plates being 
equal, the influence of distance upon its action is the same. 

89. The total amount of action under condition a, at what- 
ever position it is taken, greatly exceeds the total amount of 
action under ^ or c: but the ratio of the difference between 



Voltaic BatterieSi 8jc. 1 39 

the amount of action obtained at any of the three different 
positions in a is the same as the ratio found for these positions 
respectively in h and c, 

90. 12 : 26 (in c) : : 21 : 4!5'5 (in h) being as near an ap- 
proach to 46, the real number, as could be looked for in ac- 
tual experiment ; and the same ratios are maintained with no 
material alteration throughout. 

91. These preliminary trials show, therefore, that I may 
select any-sized couple which may appear most convenient 
for the following more extended experiments upon the effects 
of distance ; and that the results obtained by the couple now 
to be used will be true equally for this one condition and for 
every other as regards the dimensions of the couple em- 
ployed. 

92. To facilitate references to positions and numbers in 
the following experiments, let the mass of liquid in which 
they are conducted be represented by the following diagram, 
in which the horizontal line is supposed to pass through the 
centre of the mass contained in the graduated trough already 
described (36. p. 64), and the vertical line, also passing through 
the centre, to represent its depth. 

Fig. 1. 



H 1 1 ' 1 1— H 1— J 1 i 1 i 1- ! i i- 



10 II 12 13 14 15 16 17 18 



D 



93. The position of the fixed zinc plate is at Z, whence 
the graduation commences ; the first division being a quarter 
of an inch from the zinc, and the amount of voltaic action 
obtained at this first position is used throughout as the 
standard of comparison of the effects of distance. The plates 
used in these experiments, whether of zinc or copper, are each 
one inch square, and only that surface of the zinc plate which 
is opposite to the copper presents a clear amalgamated sur- 
face; the contrary surface, as well as the connecting wire, 
being well covered with wax to preclude the contact of the 
acid, and to restrict its action to the clear amalgamated sur- 
face alone. But both surfaces of the copper are clear, and 
consequently brought into operation. 

94. The experiments are first gone through with an acid 
mixture composed of 1 part by measure of sulphuric acid, and 
100 of water, its specific gravity being 1*013; and are after- 



140 



Mr. C. Binks on Electricity, 



wards repeated with other acid mixtures of the strength 
stated in the subjoined table. The copper plate being move- 
able at pleasure, is fixed, first, at the nearest position to the 
zinc, and afterwards in succession at each succeeding position 
marked upon the horizontal line. All other particulars af- 
fecting such experiments have already been sufficiently ad- 
verted to throughout section 3rd, and the observances there 
stated as necessary being fully discussed in that section, will 
in no instance be restated or again referred to in the course 
of the details that now follow. The amount of voltaic action 
obtained at each position, is estimated by the length of time 
in seconds required for the production of J^th of a cubic 
inch of the hydrogen which is evolved from the copper plate. 

95. Table showing the effects of distance, (No. 5.), in 
which the comparative amount of voltaic action is estimated 
by the length of time in seconds required for the production 
of one measure of gas. 



Distance, in 


Proportions by measure of the acid and water. 


inches, of the 


and specific gravity of the mixtures. Tempera- 


two plates 


ture 55° Fahrenheit. 


from one 
another. 


(■ 


1 part acid, 


3 parts acid, 


C parts acid, ) 9 parts acid. 1 


f 1 


100 water. 


100 water. 


100 water. 


100 water. 




Sp. gr. 1-013. 


Sp.gr. 1-034. 


Sp. gr. 1-OlS. 


Sp. gr. 1-090. 


Time. 


Time. 


Time. 


Time. 


■k 


180" 


85" 


60" 


45" 


1 


245 


135 


110 


95 


2 


370 


170 


120 


120 


4 


375 


155* 


125 


125 


6 


345* 


170 


120« 


125 


8 


400 


170 


130 


125 


10 


460 


170 


130 


140 


13 


485 


185 


130 


145 


14 


515 


200 


145 


145 


16 


530 


205 


145 


145 


18 


545 


215 


165 


130* 


20 


590 


220 


165 


145 


22 


640 


230 


165 


145 


24 


655 


235 


165 


145 


26 


660 


265 


1.90 


145 


28 


680 


295 


190 


145 


30 


690 


290 


190 


170 


32 


790 


300 


190 


200 


34 


805 


310 


220 


210 


36 


825 


360 


220 


170 


38 


885 


365 


200 


170 


40 


900 


370 


230 


170 


42 


910 370 


240 


170 


44 


920 370 


240 


170 



96. The results which are registered in this table were 



Voltaic Batteries, Sfc. l^l 

those which were obtained tjie latest of all from the experi- 
ments gone through to determine the law of distance. No 
reliance was placed upon the first attempts made to deter- 
mine this question, nor upon any, till by innumerable repe- 
titions of experiments, and a perfect familiarity with the pre- 
cautions necessary to be observed in their course, I had be- 
come assured that the whole were accurately performed, and 
that by the regulations adopted every possible or probable 
source of error likely to arise from the method here employed 
was precluded. The above results may therefore be con- 
sidered to show correctly the peculiar phaenomena attendant 
upon voltaic action, in the kind of arrangement here brought 
into action. 

97. The first consideration which naturally follows a re- 
view of the above table, is that of the singular difference in 
the effects of distance upon voltaic action ; as those effects 
are determined by this method of experimenting, and those 
already deduced by the indications of the magnetic needle. 
Referring to the nearest authority at hand, I find that the law 
of distance as determined by the needle is as follows : 

98. " The deflection produced by a pair of plates in an 
acid solution of uniform strength varies inversely as the square 
root of the distance between them, a law previously established 
by Gumming. Thus, if a plate of zinc be placed successively 
at 1, 4 and 9 inches from a plate of copper, the deflecting 
powers will be in the ratio of 3, 2, and 1 ; that is, only twice 
as great at 1 inch as at 4, and only three times as great at 
1 inch as at 9*." 

99. As the magnetic galvanometer, of whatever construc- 
tion, is employed as a measurer only of comparative quantities 
of electricity, and not of the absolute quantity evolved by 
any arrangement, it is in this relation merely that the indica- 
tions of that instrument are now brought into comparison 
with those afforded by the method here used for the same 
purpose. When the quantities of electricity evolved at the 
several distances are estimated by the indications of the 
needle (that is, by their power to deflect the needle, in op- 
position to the power of the earth's magnetism, or to any other 
power substituted for it, as in the torsion galvanometer) then 
those quantities differ from one another by the rate just stated ; 
but when estimated directly by the quantities of matter ex- 
pended in producing them (on which principle the plan now 
used is founded), then they differ from one another at these 
several distances by a rate totally different from that de- 

* Dr. Ritchie. 



1 4S Mr. C. Binks on Electricity^ 

termined by the indications of the needle ; thus placing the 
results of these two methods of estimating such effects com- 
pletely at variance. 

100. On referring to the above table it will be seen that 
no such law, nor any making the most remote approach to it, 
can be deduced from the results obtained by the present me- 
thod of testing such pheenomena. 

101. The difference between the degrees of voltaic action 
obtained at the first position, and at the last, in the first co- 
lumn of this table, amounts only to the difference between 
5 and 1, nearly; the voltaic action yielded at the first or 
nearest position being about five times greater than that 
yielded at the most remote. The distance from one another 
of the two plates at the first position is \ of an inch, and at 
the last is 44? inches, and these distances comparatively 
are as 1 and 44 x 4 or 176 ; the distance of the two plates 
from one another being 176 times greater at the last than at 
the first position. 

102. Now had the law of distance found by the method 
here employed been the same as that determined by the mag- 
netic galvanometer, we should have had the amount of action 
at the first position greater than that at the last, by the square 
root of the difference in their distances, or by the square 
root of 176; but in actual experiment it is only 5 times 
greater instead of about 1 3 times, in round numbers. 

103. This discrepancy in the results obtained by these two 
methods, in neither of which there is reason to doubt the 
correctness of the observations, leads to the suspicion that 
either the one or the other of them is an incorrect measure 
of comparative quantities of voltaic electricity, or that both 
are unfit to be applied to that purpose ; or at least are im- 
perfect in their indications; a conjecture which has given 
rise to the inquiry contained in the second part of this paper 
as already mentioned (13.). A comparison between these 
two methods will then be instituted, when it will be shown 
that there is reason to conclude that the needle does not take 
cognizance of the 'whole effects resulting from voltaic action, 
but only of a part of its attendant phaenomena ; and when 
also an attempt will be made, experimentally, to distinguish 
between the two kinds of action induced by such voltaic ar- 
rangements, of which each method is suspected to be respect- 
ively the measurer. But not further to anticipate that inquiry 
at this moment, I proceed to examine some other results 
afforded by tliis table. 

104. The difference between the amount of action obtained 
at the first and last positions has been seen to be as 5 to 1 



Voltaic Batteries, S^c. 143 

with the acid mixture of the first strength ; but it will be ob- 
served that this difference is progressively less as the mixture 
increases in strength. With the second mixture the differ- 
ence is about 41 to 1 ; with the third it is 4 to 1 ; and with 
the fourth it is 3f to one nearly — showing that the stronger 
the acid, or the greater its density, or the greater the activity 
of the generating agents, the less marked are the effects, in 
decreased action, caused by the difference in the relative di- 
stance of the two plates. 

105. Again, it is observable that the decrease in action oc- 
casioned by increased distance does not proceed at a rate cor- 
responding to that increase in distance, as the copper plate is 
removed successively to each position from end to end. The 
greatest effects of this removal through an equal distance oc- 
cur in the first two or three positions in every column ; after 
which the effects of removal are much less marked through- 
out. 

106. At those positions distinguished by an asterisk, there 
occurs a slight increase of action compared with the amount 
immediately preceding it, instead of a decrease as might have 
l)een expected. A similar anomaly, though not to the same 
extent, presents itself at several successive positions through- 
out every column, where the voltaic action appears to al- 
ternate, or to be suspended between increase and decrease 
in its amount, compared with the amounts obtained at the ad- 
jacent positions. Taking the first column by way of example, 
it will be seen that scarcely in any two instances does the re- 
moval of the plate through an equal distance produce an equal 
effect in the resulting action. The difference in effect caused 
by removing the plate from 8 inches to 10 amounts to 60", 
whilst that yielded by the change from 10 to 12 amounts only 
to 25". The following table, derived from the first column above, 
will serve to show the nature and extent of this alternation 
more clearly. The first line contains the successive distances 
to which the plate is removed ; the second, the difference be- 
tween the amount of decrease obtained at each position and 
the one preceding it. 

Table (No. 6.) 

107. (Distance of the two plates from one another, by suc- 
cessive equal steps of two inches each). 

10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 

42, 44. 
(Amount of decrease resulting from increased distance, ob- 
tained at each position, compared with the decrease at that 
immediately preceding). 



144) Mr. C. Binks on Electricity, 

60", 25", 35", 15", 15", 45", 50", 15", 5", 20', 10", 100", 15", 
20", 60'', 15'^ 10", 10". 

108. This peculiar result is equally, or even more, obvious 
in the remaining columns of the former table, No. 5 ; and it 
is observable that the particular positions at which the alter- 
nation occurs are different in each. In the latter columns, 
in which (by reason of the greater activity of the action, the 
time over which each experiment extends is progressively 
shorter), the difference in many instances is so little, if any, 
as to be scarcely discernible ; and they consequently present 
at severatl positions a series of numbers equal in amount and 
following each other in succession. 

109. It was first attempted to arrive at the law of distance, 
by the results afforded at fewer and more remote positions of 
the plates, than those given in the above tables ; for instance, 
the positions were taken at ^ of an inch, 1 inch, 4, 12 and 24 
inches ; and the amounts of action obtained at these presented a 
very regular decrease corresponding to the increase in distance. 
But some occasions arose, in which it became necessary to 
test the action of the plates at other positions intermediate to 
those already tried, when the results obtained were occasion- 
ally so greatly at variance with any anticipated by the former 
trials, that it became necessary to carry the copper plates 
through shorter successive positions from end to end, to de- 
termine whether or not those which had thus been accidentally 
detected were merely the result of accident, or of some error 
in the method of observation, or were in fact part of the gene- 
ral phasnomena attendant upon the voltaic action, as it takes 
place in the kind of arrangements here brought into opera- 
tion. Hence the long columns of observations contained in 
the former table No. 5, in the place of which it might have 
been presumed beforehand, that a very few experiments com- 
paratively would have been equally competent to decide the 
point in question, viz. the effects of distance. 

110. I should have continued, as at first, to attribute these 
unlooked for results to some accidental circumstance, had not 
their invariable recurrence under like conditions of experiment, 
shown that they had some connexion, whatever that might 
be, with the general phaenomena attending these operations, 
and were due neither to inaccuracy nor to accident. 

111. It might be suspected, among other attempts to ac- 
count for it, that the plan here resorted to (see 64) of chan- 
ging the zinc plate after every two or three immersions, might 
have some share in producing this apparent alternation in 
eflfect. But the same results follow precisely if one plate only 



Voltaic BatterieS) S^c, 145 

be used throughout. Or, again, that it might arise in part from 
the practice of determining the measure of hydrogen, sometimes 
by a division near the top of the long tubular meter here used, 
and sometimes at the bottom of it ; under which different 
circumstances, the volume of an equal measure of gas would 
be a little different by reason of the varying strain upon its elas- 
ticity. But the trifling variation that might have arisen from 
this cause, was also avoided by invariably refilling the meter 
after each single experiment, so that the y^th of a cubic inch 
of gas was always under a uniform pressure. But in short, 
after the utmost attention to the subject, I could discover no 
peculiarity attending this particular method of experimenting 
to which this effect could be attributed, with the most remote 
appearance of probability. 

112. Sueh alternation then must be considered as apart 
of the general phaenomena attending operations of this kind, 
however unexpected or inexplicable it may be in the present 
state of our acquaintance with the subject generally. 

113. I was unwilling in the first instance to register the re- 
sults as they stand above, expecting that every succeeding re- 
petition of experiment would show a greater regularity in the 
operation of the arrangements ; or such a regularity as, by 
preconceived notions, derived chiefly from the law above quo- 
ted (98), I had been led to anticipate. It is obvious however, 
that the operations brought into exercise by voltaic arrange- 
ments of this description at least, are of a mixed and compli- 
cated kind, influenced in some parts by causes as yet unde- 
tected, and are certainly such as cannot be fully included in 
any law similar to that just alluded to. The removing of the 
plates further from one another does not affect their action, 
merely by decreasing its amount, much less does that decrease 
occur in the ratio stated in that law. 

114. Perceiving at this stage of the inquiry no satisfactory 
or probable way of accounting for this peculiar result, I pro- 
ceed on to the further experiments, in which it will be seen 
that other indications of the same phaenomenon can be de- 
tected in every direction, whether or not the results finally 
obtained may be considered in every respect as contributing 
satisfactorily to its explanation. 

[To be continued.] 



Phil, Mag, S. 3. Vol. 13. No. 80. Aug, 1838. 



[ 146 ] 
X X . Proceedings of Learned Societ ies. 

ROYAL SOCIETY. 

[Continued from vol. xii. p. 433.] 
April 26, A Paper was read, entitled, " An Account of a line of 
-^^ Levels carried across Northern Syria, from the Me- 
diterranean Sea to the River Euphrates." By William Taylor Thom- 
son, Esq., w^ith Geological and Botanical Notes, by William Ains- 
worth, Esq. Communicated by Captain Beaufort, R.N„ F.R.S., &c. 

The operation of carrying a line of levels across Northern Syria, 
from the Mediterranean sea to the river Euphrates, was undertaken 
by Colonel Chesney, at the time he commanded the expedition sent 
to that river in the year 1835, chiefly with a view to determine the 
capabilities of the intervening country for the establishment of com- 
munications by roads, railways, or canals ; but it was expected also 
that the examination would aflford information of much historical 
and geographical interest. It was commenced in August of the 
same year, by Lieutenant Murphy and Mr. Thomson, assisted by 
Sergeant Lyne, R.E., Gunner Waddell, and some Maltese : but 
most of the party being disabled by sickness, and their numbers re- 
duced by deaths and removals, the levelling was at length conduct- 
ed principally by Mr. Thomson, with the assistance, in the latter 
part of the work, of Mr. Elliott, commonly called Dervish Ali. The 
result of this great labour was to determine the bed of the Euphrates 
to be 628 feet above the level of the Mediterranean. 

The whole of the district over which the line of levels was carried 
naturally divides itself into four regions, each of which is character- 
ized by its relative elevation, its peculiar geological structure, its 
vegetation, and the manners and habits of its population. 

The first region, commencing from the Euphrates, comprises the 
country of the upper chalk and conide limestones, which averages 
an elevation of 1300 feet, and is but slightly undulated. The soil 
is light, somewhat stony, and of no great depth, and is highly pro- 
ductive in crops of corn and cotton. These uplands are inhabited by 
stationary Turcomans and Arabs, who are a mixed race of Fellahs. 
The large plains of this region are studded over in every direction 
with numerous mounds, of a more or less circular form, called by 
the Arabs Tets, and by the Turcomans Heuks, the origin of which 
appears to be partly natural and partly artificial. A village is found 
at the foot of almost every one of these monticules. 

The second region comprises the country of ostracite limestone 
and feldspath pyroxenic rocks, in the valley of Ghuidaries and the 
Aphrean, having a mean elevation of 450 feet. This district is ex- 
tremely fertile, for the most part cultivated, and inhabited by agri- 
cultural Kurds. 

The third region is the lacustrine plain of Umk, elevated about 
305 feet above the Mediterranean, and covered, for the most part, 
with the gramineous plants which feed the flocks of the pastoral and 
nomadic Turcomans. 



Prof. Faraday's Researches in Electricity. 14-7 

The fourth region, formed by the valley of Antioch, is rocky, 
irregular, and varying from elevations of 220 to 440 feet. It com- 
prises also the alluvial plain of the Orontes, which gradually sinks 
to the level of the Mediterranean. This latter district is covered 
with shrubs, which are chiefly evergreens ; and inhabited by a few 
families of Syrians, who, in these picturesque solitudes, chiefly fol- 
low mysterious rites, presenting a mixture of Mahomedanism and 
Christianity. 

It appears, from the examination of this line of country, that 
there here exist two distinct regions, the one low and already fur- 
nished with the means of water transport ; and the other elevated, 
where the waters, which are lost in the valley of Aleppo, might be 
turned with facility into an artificial channel. Both regions are re- 
markably level, and present, when separately viewed, very few difli- 
culties to be overcome for the construction of artificial roads. 

May 3. — A paper was read, entitled, " Supplementary Note to 
the Eleventh Series of Experimental Researches in Electricity." 
By Michael Faraday, Esq., D.C.L., F.R.S., &c.* 

The author describes, in this supplementary note, experiments 
made with the view of determining the specific inductive capacities 
of dielectrics, by means of an apparatus of the following form. Three 
circular brass plates were mounted, side by side, on insulated pillars; 
the middle one was fixed, but the two outer plates were moveable on 
slides, so that all three could be brought with their sides almost into 
contact, or separated to any required distance. Two gold leaves 
were suspended in a glass jar from insulated wires, connecting each 
of the leaves respectively with the adjacent outer plate. The amount 
of disturbance in the electric equilibrium of the outer plates pro- 
duced by interposing a plate of the dielectric substance to be tried, 
after charging the middle plate, was taken as a measure of the spe- 
cific inductive capacity of that dielectric. By varying the size and 
distances of the plates, and also the distance of the gold leaves from 
one another, new conditions are supplied for the more exact deter- 
mination of the relative inductive powers of dielectrics of every de- 
scription ; and by sufficiently reducing the dimensions of the instru- 
ment, it may be rendered applicable to comparatively small masses 
of dielectrics, such as crystals, and even diamonds. An instrument 
capable of such universal application the author proposes to desig- 
nate by the name of Differential Inductometer. 

Also read, a Letter addressed to P. M. Roget, M.D., Secretary 
to the Royal Society, by James Ivory, Esq., F.R.S., accompanying 
a paper on Astronomical Refractions. Communicated by Dr. Roget. 

The author adverts in this letter to the attempts made by New- 
ton to solve the problem of atmospherical refractions, which were 
baffled by the experience that the observed quantities fall far short 
of the theoretical deductions ; whence he justly inferred that some 
new cause must be sought for capable of effecting that change in 

* An abstract of Prof. Faraday's Eleventh Series of Researches was 
given in Lond. and Edinb. Phil. Mag. vol. xii. p. 338. — Edit. 

L2 



148 Royal Society, 

the density of the lower part of the atmosphere which is reqiiired for 
reconciling theory with observation. It becomes necessary, in par- 
ticular, to investigate the law according to which the temperature 
diminishes as the height increases. The initial value of the rate of 
diminution has to be determined by experiment ; and the introduc- 
tion of this new element into the equation of an atmosphere in equi- 
librium must be an approach to the true solution of the problem of 
the refractions, and is indispensable if arbitrary assumptions are to 
be avoided. The author proceeds to notice Laplace's solution, 
which, though highly ingenious, is nevertheless hypothetical ; and 
he adverts to the want of precision exhibited in Biot's dissertation 
on the influence which the presence of aqueous vapour in the air 
has on the refractions : but refers to the paper which accompanies 
his letter for the further explanation of his views on this subject. 

A paper was also in part read, entitled, " On the Theory of the 
Astronomical Refractions," by James Ivory, Esq., K.H., M.A., 
F.R.S., &c. 

May 10. — The reading of Mr. Ivory's paper " On the Theory of 
the Astronomical Refractions," was resumed. 

May 24. — The reading of the paper by Mr. Ivory, " On the 
Theory of the Astronomical Refractions," was concluded. 

In this communication, the author, after stating that the mean 
refractions are the object of investigation, and fully defining what 
he understands by this term, gives an historical review of what has 
been done up to the present time on this very important subject. 
Having stated that the foundation of the theory of astronomical re- 
fractions was laid by Dominique Cassini, he deduces on Cassini's 
hypothesis (that of an homogeneous atmosphere) a formula for the 
refraction, which agrees exactly with that of La Place, employed in 
computing the first part of the table of mean refractions, published 
by the French Board of Longitude. 

The labours of our immortal countryman Newton, in this vast 
field of inquiry, are next reviewed. As the density of the atmo- 
sphere in ascending decreases gradually, the path described by a ray 
from a star, in its passage through the atmosphere, is not a straight 
line, as it would be on Cassini's hypothesis, but is a curve more and 
more inflected towards the earth's centre. In the Principia there is 
found whatever is necessary for determining the nature of this curve, 
and, consequently, for solving the problem of the astronomical re- 
fractions, which consists in ascertaining the difference between the 
direction of light when it enters the atmosphere, and its ultimate 
direction when it arrives at the earth's surface. 

On the principles established in the second section of the Prin- 
cipia, the author deduces equations requisite for the solution of the 
problem of astronomical refractions, and remarks that these equations 
are perfectly general, and will apply in any constitution of the at- 
mosphere that may be adopted. In this investigation, in preference 
to employing functions with peculiar properties to express the mole- 
cular action, the manner in which the forces act has been consider- 
ed. When the light, in passing through the atmosphere, arrives at 



Mr. Ivory on the Theory of the Astronomical "Refractions. 149 

a surface of increased density, it receives an impulse which may be 
considered as instantaneous; and this impulse being distributed over 
the breadth of a stratum of uniform density, ascertains the centripetal 
force tending to the earth's centre, by the action of which the tra- 
jectory is described. 

It appears, that Newton himself was the first to apply this new 
method to the problem of the astronomical refractions. In his first 
attempt he assumes that the densities decrease in ascending, in the 
same proportion as the distances from the earth's centre increase. 
On this supposition the author investigates a formula, which M. Biot 
has also obtained, and which is equivalent to the construction com- 
municated by Newton to Flamsteed. On this basis a table was 
computed and communicated to Flamsteed; but Newton subsequent- 
ly informed Flamsteed that he did not intend to publish it, in con- 
sequence of a serious objection to the supposed scale of densities. 
Adopting the principles in the twenty-second proposition of the 
second book of his Principia, Newton, it appears, succeeded at length 
in computing a second table of refractions, which he likewise com- 
municated to Flamsteed, and which, there is every reason to think, 
is the same which he gave to Halley, and which was inserted by that 
astronomer in the Philosophical Transactions for 1721. As the de- 
termining whether the two tables are identical is a question of much 
interest, the author enters very fully into it, and, from the results 
of elaborate calculations, concludes that Halley's table is no other 
than the one which Newton calculated on the supposition that the 
densities in the atmosphere are proportional to the pressures. He 
remarks that, as far as the mathematics are concerned, the problem 
of the astronomical refractions was fully mastered by Newton. 

After referring to the labours of Brook Taylor, Kramp, and Thomas 
Simpson, the author again adverts to Newton's views, remarking 
that, in assigning the rarefaction of the lower region of the atmo- 
sphere by heat as the cause why the calculated refractions near the 
horizon so much exceeded the observed, as was found to be the case, 
Newton had assigned the true cause ; but that he had no clear con- 
ception of the manner in which the density in the lower region is 
altered by the agency of heat; and he considers that nearly the same 
ignorance in that respect still prevails. 

The two atmospheres, with densities decreasing in arithmetical 
and geometrical progression, which, it now appears, were imagined 
by Newton, and which have been discussed by Thomas Simpson and 
other geometers, are found, when the same elements are employed, 
to bring out horizontal refractions on opposite sides of the observed 
quantities. La Place conjectured that an intermediate atmosphere 
which should partake of the nature of both, and should agree with 
observation in the horizontal refraction, would approach nearly to 
the true atmosphere. If recourse be had to the algebraical expres- 
sions of La Place, it will be found that the atmosphere he proposes 
is one of which the density is the product of two terms, the one 
taken from an arithmetical, the other from a geometrical series; the 
effect of which combination is to introduce a supernumerary con- 



160 Royal Society, 

stant, by means of which the horizontal refraction is made to agree 
with the true quantity. The author considers, with Dr. Brinkley, 
that the French table, founded on La Place's investigation, is only a 
little less empirical than the other tables, and that the hypothesis of 
La Place does not appear to possess any superiority over other sup- 
posed constitutions of the atmosphere in leading to a better and less 
exceptionable theory. 

After eulogizing Bessel's tables of mean refractions, published in 
his Tabulce RegiomontancE, the author refers to his own paper in the 
Philosophical Transactions for 1823 *. In this paper the refractions 
are deduced entirely from the very simple formula, — 

i:^,=i-fa-c ) 

in which /5 stands for the dilatation of air or gas by heat, r' and r" 
for the temperature at the earth's surface, and at any height above 
it, and c~" for the density of the air at that height in parts of its 
density at the surface. If this formula be verified at the earth's sur- 
face in any invariable atmosphere, by giving a proper value to the 
constant/, it will still hold, at least with a very small deviation from 
exactness, at a great elevation; and this is immediately shown. 

This manner of arriving at the constitution of the atmosphere is 
contrasted with the procedure of M. Biot of transforming an alge- 
braical formula, for the express purpose of bringing out a given re- 
sult. As the problem in the 3Iecamque Celeste is solved by means 
of an interpolated atmosphere between two others; as in Mr. Ivory's 
paper of 1823, there is no allusion to such an atmosphere; and as 
the table in that paper is essentially different from all the tables 
computed by other methods, he contends that all these must be suf- 
ficient to stamp an appropriate character on his solution of the pro- 
blem. But if ingenuity could trace some relation, in respect of the 
algebraic expression, between the paper of 1823 and La Place's cal- 
culations, he considers that it is not difficult to find, between the 
same paper and the view of the problem taken by the author of the 
Principia in 1696, an analogy much more simple and striking. 
Newton having solved the problem, on the supposition that the den- 
sity of the air is produced solely by pressure, and having found that 
the refractions thus obtained greatly exceeded the observed quantities 
near the horizon, inferred, in the true spirit of research, that there 
must be some cause not taken into account, such as the agency of 
heat, which should produce, in the lower part of the atmosphere, the 
proper degree of rarefaction necessary to reconcile the theoretical 
with the observed refractions. The author's sole intention, in intro- 
ducing the quantity y in his formula, is to cause the heat at the 
earth's surface to decrease in ascending, at the same rate that ac- 
tually obtains in nature, not before noticed by any geometer, but 
which evidently has the effect of supplying the desideratum of 
Newton. 

• Mr. Ivory gave an account of the theory of refractions enunciated in 
his paper of 1823, in the Phil. Mag. First Series, vol. Ixiii. p. 420.— Edit. 



Mr. Ivoiy on the Theot'y of the Astronomical Refractions. 151 

The author considers, that the comparison of the table in the pa- 
per of 1823, with the best observations that could be procured at the 
time of publication, was satisfactory ; and after the publication of 
the Tabula Regiomontance, he found that the table agreed with 
Bessel's observed refractions to the distance of 88° from the zenith, 
with such small discrepancies as may be supposed to exist in the 
observations themselves. 

The paper in the Philosophical Transactions for 1823, however, 
takes into account only the rate at which the densities, in a mean 
atmosphere, vary at the surface of the earth ; but, in the present 
communication, the author proposes to effect the complete solution 
of the problem, by estimating the effect of all the quantities on which 
the density at any height depends. For this purpose, he finds it ne- 
cessary to employ functions of a particular kind ; and then gives a 
formula, one part of which consists of a series of these functions, for 
the complete expression of the temperature of an atmosphere in 
equilibrium ; the intention of assuming this formula being to ex- 
press the temperature in terms of such a form as will produce, in the 
refraction, independent parts that decrease rapidly. By this means 
he proceeds in the analytical investigation of the problem in its more 
comprehensive form, and deduces two equations on which its solu- 
tion depends. 

The first of these contains the law according to which the heat 
decreases as the height above the earth's surface increases ; and the 
second determines the perpendicular ascent, when the difference of 
the pressures and of the temperatures at its upper and lower extre- 
mity have been found. If the latter, with a slight transformation, 
be multiplied by the proper factor, representing the variable force of 
gravity in different latitudes, it becomes identical with the usual 
barometric formula, all its minutest corrections included; and it has 
this advantage ; that, whereas the usual formula is investigated on 
the arbitrary assumption, that the temperature is constant at all the 
points of an elevation, and equal to the mean of the temperatures at 
the two extremities, this formula is strictly deduced from the gene- 
ral properties of an atmosphere in equilibrium. 

Having determined, from experimental results, the values of cer- 
tain constants in these formulae, — first, in an atmosphere of dry air, 
and, secondly, in an atmosphere of air mixed with aqueous vapour, 
the author remarks, that the analytical theory agrees in every re- 
spect with the real properties of the atmosphere, as far as these have 
been ascertained. 

The object of Mr. Ivory's further investigation is to show, that 
the same theory represents the astronomical refractions with a 
fidelity that can be deemed imperfect only as far as the values of 
particular constants, which can only be determined by experiment, 
are liable to the charge of inaccuracy. He therefore proceeds to 
determine, from the formulae previously deduced, the refraction of a 
star in terms of its apparent zenith distance. For this purpose, the 
differential equations are transformed by the introduction of new 
symbols ; the limits of certain terms are determined previously to 



152 Royal Society. 

their being neglected ; and the equation is finally reduced to a form, 
in which the remaining operations consist in investigating the inte- 
grals of four expressions, and in subsequently assigning their nume- 
rical values. Great skill is displayed in conducting these intricate 
investigations ; and after going through the most laborious calcula- 
tions and computations, the author exhibits a table of theoretical re- 
fractions, deduced solely from the phenomena of the atmosphere, 
for zenith distances, extending from 10° to 89|°. These refractions 
are compared with those in Bessel's table, in the Tabulte Regiomon- 
tancE, and also with those in the table in the Connaissance des Temps. 
From this comparison, it appears, that the three tables agree within 
less than 1", as far as 80° from the zenith: from 80° to 88° of zenith 
distance, the numbers in the French table exceed those in Bessel's, 
the excess being 2" at 84°, and 4" at 88° ; and with a single excep- 
tion at 88°, (probably, judging from the character of the adjacent 
number, arising from an error of computation,) the refractions in 
the new table are nearer to Bessel's than those in the French table ; 
but when the zenith distance is greater than 80°, the author con- 
siders the accuracy of the French table questionable, both on account 
of the hypothetical law of the densities, and because the quantity 
assumed for the horizontal refraction is uncertain. 

After giving a few examples, illustrative of the use of the new 
table, the author inquires how far the refractions are likely to be 
affected by the term which it was found necessary to leave out, be- 
cause the present state of our knowledge of the phenomena of the 
atmosphere made it impossible to determine the coefficient by which 
it is multiplied. For this purpose, the variable part of that term 
has been computed for every half degree, from 85° to 88°, and the 
results are exhibited in a table. From this it appears, that this co- 
efficient, although considerably less than that of the preceding terra, 
may still have some influence on the refractions at very low alti- 
tudes. The mean refraction in Bessel's table, and in the new table, 
can hardly be supposed to differ 2" from the true quantity, which 
would Umit the coefficient in question to be less than one-tenth. It 
is a matter of some importance to obtain a near value of this coeffi- 
cient ; and it is probable that this can be accomplished in no other 
way, than by searching out such values of the two coefficients as will 
best represent many good observed refractions at altitudes less than 
5°. If such values were found, our knowledge of the decrease of heat 
in ascending in the atmosphere would be improved, and the measure- 
ment of heights by the barometer would be made more perfect. 

At the end of the paper is given a table of mean refractions for 
the temperature 50° Fahr. and barometric pressure 30 inches, at 
every degree from 0° to 70° zenith distance, and at every 10' from 
70° to the horizon ; and tables of the corrections requisite for va- 
riations of the thermometer and barometer are subjoined. 



[ 153 ] 
XXI. Intelligence and Miscellaneous Articles. 

CAUSE OF THE CIRCULATION OF THE CHARA. 

M DONNE states that he thinks he has discovered the cause 
• of circulation in plants, of which the Chara is a remarkable 
example. Contrary to the opinion of several authors who have attri- 
buted this circulation to physical agents, M. Donne supposed that its 
cause might be found in an organic disposition, and with this view 
entered into an examination, the result of which he thus states : — 

" After having carefully taken off the outer coating of a tube of 
Chara hispida, and deprived it of the carbonate of lime, which inter- 
feres with its transparency, I submit it under the microscope to a 
methodical and graduated pressure, by the aid of M. Purkinje's 
press. This pressure immediately detaches a great number of 
granules. Little strings, formed of 5, 6, or more granules, are then 
seen to put themselves in motion, turn round, and then stop if they 
are not carried away by the current of the fluid ; other granules are 
completely detached from one another, and free from all adhesion ; 
amongst these are seen some which have a rotary movement, more 
or less rapid, independent of the movement of general circulation ; 
some turn round on themselves without changing place ; others are 
carried along by the current, but still preserving their spontaneous 
rotary movement. 

" These small bodies are therefore endowed with a peculiar power, 
which they obey when they are free, but which react on the liquid 
in which they are immersed when they are fixed. 

" The rotary motion I speak of, is independent of that of the 
liquid in circulation ; it is often very rapid indeed in comparison 
with the motion of circulation, and takes place when the circulation 
is slowest or has even ceased : it is not a rare case to see two gra- 
nules near one another moving in a contrary direction ; the follow- 
ing experiment will show this fact in a decisive manner, 

" By pressing out the sap from a tube of Chara upon a piece of 
glass, and submitting this drop of liquid to inspection under the 
microscope, it is found to be composed, not only of the fluid and 
of white particles which were in circulation, but of a certain quan- 
tity of green granules, which the pressure has detached from the 
sides of the tube ; the greater number of these granules are strung 
together, and no motion is to be discovered in them, nor in the free 
isolated granules spread over the surface of the glass. This is not 
the case with the large oily or albuminous drops which the interior 
fluid of the Chara forms upon difiusing itself : it is seldom that in 
some of these drops, the transparency of which is unfortunately 
troubled by a number of small grains, one or several green granules 
are not found endowed with the same spontaneous rotary motion 
which takes place in the interior of the tube itself ; these granules 
being in their natural fluid have preserved all their properties, whilst 
the others may be considered as dead. 



154 Intelligence and Miscellaneous Articles. 

" It- is impossible," continues- M. Donne, " not to remark the 
striking analogy which these facts establish between the corpuscles 
ranged in regular and fixed series on the internal sides of all vege- 
table cells where the double circulation of a fluid has been observed, 
and the vibratile organs of animals, to which attention has been 
directed since the work of MM. Purkinje and Valentine : this 
analogy is the more complete, as the vibratile organs of the mu- 
cous membranes separate themselves, as I have shown, into parti- 
cles, when the motion may be observed to continue often for more 
than twenty-four hours. 

" I examined if there existed vibratory hairs on the surface of 
the granules endowed with the spontaneous movement which I have 
just described, but was not able to discover any, although I employed 
a power of 500 diameters with a good light. I thought I saw a 
brilliant circle round the granules, but cannot affirm any thing more 
on this point. 

" I must add that all the agents which stop the circulation of the 
Chara, also destroy the rotary motion of the granules." — L'lnstitut, 
April 1838. 



ACTION OF PLANTS ON THE AZOTE OF THE ATMOSPHERE. 

M. Boussingault has entered into an investigation in order to as- 
certain whether plants absorb the azote of the atmosphere. In 
these researches he has employed analysis, and compared the com- 
position of the seeds with the composition of the results of their 
growth, obtained at the expense only of water and air. Although 
these experiments were undertaken specially with a view to examine 
into the question as to azote, they also determine with precision the 
elements lost or gained by clover seed and wheat, during their ger- 
mination and vegetation. These plants were vegetated in air con- 
tinually renewed, and well washed to deprive it of all dust, watered 
with distilled water, and cultivated in a siliceous sand. The follow- 
ing are the results of this investigation. 

1 . That clover seed and wheat during germination neither gain 
nor lose azote. 

'2. That these seeds lose carbon, hydrogen, and oxygen, and that 
the quantity of each of these elements varies at different periods of 
their germination. 

3. That during the culture of clover seed in a soil absolutely free 
from manure and only under the influence of water and air, this 
plant talces up carbon, hydrogen, and oxygen, and an appreciable 
quantity of azote. 

4. That wheat cultivated under precisely the same circum- 
stances also takes from the water and the air, hydrogen and oxy- 
gen ; but after a culture of three months not the slightest gain or 
loss of azote could be detected by analysis. 

The following is the result of M. Payen's examination on azote 
contained in plants. 



Intelligence and Miscellaneous Articles. ISS 

That the radicals of all plants contain an azotic substance in suf- 
ficient abundance to give out upon distillation free or carbonated 
ammonia. 

That every organ in a state of growth or in the course of deve- 
lopment contains an abundance of an azotized substance ; that as 
the organ becomes developed, the azotized substance decreases in 
quantity in comparison to the non-azotized substance, which latter 
becomes by degrees altogether predominant. From a number of 
examinations he concludes this fact to be general ; — that the cam- 
bium contains this azotized substance in abundance, and that the 
sap is also charged with it. 

M. Payen found in passing a quantity of water through a recently 
cut stick of elder that the wood was deprived of all the azotized 
matter, which the water separated ; from this he is led to explain 
the action of all the substances employed to preserve wood which 
have the effects of acting upon the azotized substance, coagulating 
it, and rendering it insoluble in water. — L'Institut, February 1838. 
No. 224. 

PROrORTIONS OF ANIMAL AND EARTHY MATTER IN HUMAN 

BONES. 

Dr. G. O. Rees read a paper on the above subject, on the 8th of 
May, at a meeting of the Medico-Chirurgical Society. 

The author, after alluding to the jjrecautions necessary to be ob- 
served in the analysis of bone, proceeded to recount the results of 
his examinations. The solid parts of the femur, tibia, fibula, hu- 
merus, radius, and ulna were chosen for analysis ; also the squa- 
mous portion of the temporal bone, the arch of a dorsal vertebra, 
the external crust of a rib and of the clavicle, the cora^oid process 
of the scapula, a portion of the ilium near the crest of the bone, the 
metatarsal bone of the great toe, and a part of the middle portion 
of the sternum. These bones had been similarly prepared, and were 
quite free from fat, periosteum, and cartilage, and perfectly dry. 
The long bones of the extremities were found to contain from 63 '02 
to 60" 01 per cent, of earthy matter, and the bones of the trunk from 
58'79 to 54'51 per cent. The author then mentioned the general 
conclusions to which his experiments had led him. They were as 
follows : — 

1st. The long bones of the extremities contain more earthy mat- 
ter than those of the trunk. 

2nd. The bones of the upper extremity contain somewhat more 
earthy matter than the corresponding bones of the lower extremity ; 
thus the humerus more than the femur, and the radius and ulna more 
than the tibia and fibula. 

3rd. The humerus contains more earthy matter than the radius 
and ulna, and the femur more than the tibia and fibula. 

4th. The tibia and fibula contain, as nearly as possible, the same 
proportions of earthy matter, and the radius and ulna may be con- 
sidered as alike in constitution. 

5th. The vertebra, rib, and clavicle are nearly identical as re- 



156 Intelligence and Miscellaneous Articles. 

gards the proportion of earthy matter, the ilium containing some- 
what more of earths, the scapula and sternum somewhat less, the 
sternum containing more earths than the scapula. 

6th. The bones of the head contain more earthy matter than the 
bones of the trunk, as observed by Dr. J. Davy ; but the humerus 
and other long bones approach very near in their proportion of 
earths. 

7th. The metatarsal bones may probably be ranked with those of 
the trunk in proportional constitution. 

The cancellated structure of bone is shown by the author to con- 
tain less earthy matter than the more solid parts of the same bone ; 
the canceUi of a rib contained 4 per cent, less of earths than the solid 
external crust. 

Several of the laws of relative proportion observed in the adult 
skeleton were shown to hold good in the fcetal bones*. Thus, the 
bones of the upper contain more earthy matter than those of the 
lower extremity. 

The humerus contains more earthy matter than the radius and 
ulna, and the femur more than the tibia and fibula. 

The ilium contains more, and the scapula less earthy matter than 
the clavicle or rib. 

The great difference observable in the proportional constitution 
of the adult and foetal bones, consists in the fact that the long bones 
and the bones of the head do not contain the excess of earths ob- 
served in the adult skeleton. 

The author concludes, by showing that the bones of the trunk, 
in the foetus, contain as large a proportion of earthy matter as those 
of the adult. 

ON THE AMMONIACAL AND OTHER BASIC COMPOUNDS OF THE 
COPPER AND SILVER FAMILIES. BY PROFESSOR KANE.f 
Having verified Berzelius' formula for the ammoniacal sulphate of 
copper CM sog + 2 NH3 + ho.. Dr. Kane pointed out, that, from the 
circumstances of its formation, and others, the real formula must be 
(NH3H0 + SO3) + NH3.CM0; and that by heat it loses NH3.H0. and 
leaves a compound NH3.CM o + SO3. ; by still more heat there re- 
mains 2 SO3 -f 2 CM o + NH3 or CM0.SO3. + (nHj.cm o) SO3. and by 
water there is formed the ordinary basic sulphate CM0.SO3 + 3 cmo 

-f 4 HO. 

Dr. Kane describes likewise a new basic sulphate as SO3 + 8 cm 
+ 12 HO. and he arranges these two salts as 

1 = CM 0.SO3 CM o + 2 (cm + 2 no\ 

2 = CM 0.SO3. CM o + 6 (cm + 2 ho), 

and seeks to establish an analogy with the ordinary salts of the same 
family, as 

zno. SO3 HO + 6. ho and cm o.sOj.cm o + 6 cm o. 

* The foetal bones examined by the author were deprived of fat, peri- 
osteum, and epiphysis, and were perfectly dry. 

f From the Proceedings of the Royal Irish Academy for May 28, |838; 
with corrections by the author. 



Intelligence and Miscellaneous Articles. 157 

Dr. Kane found the ammoniacal chloride of copper to be cm c^ + 
2 NH3 + no. or correctly, NH3. n c^ -|- nhj. cm o. By heat NH3H0 
is lost, and there remains NH3. h cm cl. By water there is generated 
a new basic chloride of copper, having the formula cm c/ + 4 cm o 
+ 6 HO. The common Brunswick green cm c/ + 3 cm o + 4 ho. 
Dr. Kane has obtained with 6 ho in place of 4 ho. and these oxy- 
chlorides he considers as formed on the type of the ordinary chlo- 
rides, combined with water, or with metallic oxides in other groups. 

1 — CM. c? + CM o + 2 (cm + 2 ho) 

2 — CM c/ -f 3 (cm + 2 ho) 

3 — cm c/ + cm o + 3 (cm + 2 ho). 

Dr. Kane has obtained another new oxychloride composed of cm 
cZ + 2 CM o ; taking one atom of water, it remains brown, but with 
more it forms a green powder, — the first replacing the third of cm o 
in the common oxychloride. 

When No. 2 is heated, it loses all water, but if then put into con- 
tact with water, it regains 4 ho, and becomes perfect Brunswick 
green No. 1. cm c/f. cm o + 2 (cm o + 2 ho). 

The second equivalent of oxide is, in these chlorine bodies, much 
less forcibly held than in the sulphates, but that it is differently re- 
lated to the acid than the remaining equivalents of oxide or of water 
is proved by a great- variety of facts. 

The ammoniacal nitrate of copper has the formula cmo NO5 + 
2 NH3, or (NH3.H0.) NO3 + cm nHo. hence this body contains, united 
with the copper, amidogen ; when heated it explodes, the copper and 
amidogen burning in the nitrous oxyde yielded by the nitrate of am- 
monia. To obtain some analogical evidence regarding this body. 
Dr. Kane re-examined the ammonia- sulphate and nitrate of silver, 
and found George Mitscherlich's results good. Dr. Kane, however, 
writes the formulse 

1 — (NH3.H0). SO3 + Ag. NH2 

2 — (NH3.H0) NO5 + Ag NHjj. 

This last salt, when heated, gives a beautiful decomposition ; the ni- 
trate of ammonia fuses readily, and at a temperature below that at 
which it decomposes, the amide of silver is resolved into ammonia, 
nitrogen, and metallic silver, which latter being deposited on the 
sides of the glass, from the liquid nitrate of ammonia, gives a mirror 
surface equal to that obtained by aldehyd. 

On analyzing the ammoniacal compounds of nickel. Dr. Kane 
found the results of Erdman completely verified ; but from the in- 
ferior afiinity with which the ammonia was retained, these com- 
pounds did not yield as positive results as to their influence on theory, 
as those of the copper class. 

A new substance, discovered in the course of these researches, 
may be termed a fulminating copper. It is a blue powder, decom- 
posed by heat into metallic copper, water, ammonia, and nitrogen. 
Its formula is 3 cmo + 2 NH3. + 6 ho. 

The examination of the zinc compounds has led to the discovery 



158 Intelligence and Miscellaneous Articles, 

of a considerable number of new bodies. The ammoniacal sulphate 
of zinc crystallized is 

1 — ZWO.SOj -f 2NH3 + 3 HO 

exposed to the air it effloresces, losing ho, and becomes 

2 — zwo.sog + 2 (NH3.H0). 
which, if heated, gives at 212° F. 

3 — zwo.sog + (NH3.H0.) 

but at dull redness loses still nh^.ho and leaves zwo.sog. 

If No. 1 be exposed longer to a moderate heat it loses 2 ho, and 
there remains, 

4 — zno SO3 + 2 NH3 + HO. 

If this be heated to 300°, it loses (NH3 ho) and there is 

5 — ZW0.SO3 + NH3. 
which further gives by heat 

6 — 2 (ZWO.SO3) + NH3 

from which the ammonia cannot be expelled without decomposition. 
Selecting from among these No. 2, for reduction to its rational 
formula, it becomes 

(NH3.HO.) SO3 + ZWO. (NH3.H0). 

Now the oxide of zinc from the sulphate being redissolved by pot- 
ash, there must be formed the similar compound 

K.O.SO3 + ZWO.KO. 

This cannot be obtained crystallized, for if the liquor be evaporated 
there is deposited KO.SO3, and zreo.Ko remains dissolved ; from this, 
by exposure to the air, there are gradually deposited small crystals, 
which Dr. Kane considers as being 

KO.CO2 + Z« O.COj 2 HO. 

but by heat there is carbonic acid given off, and a powder insoluble 
in water is produced, the composition of which, from Dr. Kane's exa- 
mination, appears to be 

KO.CO2 4- z«o.cOc2 + 2 z«o. 
It will be recollected, that the bicarbonate of potash is 

KO.CO2 + HO.COo. 

By treating the ammonia sulphate No. 3 or 5 by water, there is 
obtained a basic sulphate, having the formula 

zrao.soj + 6 z«o -|- 12 ho. 
which, dried and exposed to the air, slakes, and gives 

ZBO.SO3 + 6 zwo + 3 HO. 
This new salt has some remarkable relations to those already known. 
There are two ammonia chlorides of zinc. 
No. 1 , in pearly scales of a talcy lustre, consists of 

zw c/ -H 2 NH3 -f HO, 
and, when heated, gives off NH3.H0. leaving nhs.zwc/. a white 
powder. 



Meteorological Observations. 159 

No. 2 is in fine quadrangular prisms, brilliant lustre, consisting 
of 2 zw c/ + 2 NH3 4- no. or as Dr. Kane considers, zn.cl + (NH3. 
ncZ) + NH3.ZWO. which losing NH3.H0 leaves z« c/ + NH3.ZW c/. a 
white mass, fusible, congealing into a mass like gum, and volati- 
lizable. This gummy mass is likewise obtained by heating NH3ZM c/. 

There is generated by the action of water on these basic ammo- 
niacal compounds, an oxychloride of zinc of a very remarkable cha- 
racter ; it is — 

zncl ■\- Szno + 10 ho. 

dried, it is reduced at 212° to 9 ho + and by 300° to 6 ho. By 
500° all water is driven off, and there remains zncl + 6 zw o which 
exposed to the air absorbed 3 ho. Hence the general expression is 

Z« cZ + 6 ZW O + 4 HO + 2 HO + 2 HO + 2 HO 

and comparing some similar chlorides, there is, 

1 cfl.c^ + 6 HO crystallized chloride of calcium. 

2 zn cl + 6zn o — basic chloride of zinc dry. 
3hc^+6ho — strong muriatic acid. 

4 z«c/ + 6 ZM o + 10 HO — hydrated oxychloride of zinc. 

5 H c/ 4" 6 HO + 10 HO — muriatic acid with a constant boil- 

ing point. 

Another oxychloride, having the composition 

Z« C/ + 9 ZM O -f- 15 HO 

which dried and exposed to air, absorbs 6 ho. Hence it may best 
be considered as 

(zw c^ + 6 zw o -j- 12 H o) +3 (z« o no), 
giving ultimately 

(zn cl + 6 zno + 3 no) -f- 3 (zwo + ho). 



METEOROLOGICAL OBSERVATIONS FOR JUNE 1838. 

Chisivick. — June 1. Very fine: rain. 2,3. Cloudy and fine. 4. Fine: 
rain. 5. Hazy : very fine. 6. Slight haze : fine. 7. Fine. 8. Cold 
and dry. 9. Fine. 10. Cloudy and fine. 11. Hazy: rain. 12. Rain, 
with thunder. 13. Fine: heavy rain at night. 14, 15. Overcast: rain. 
16. Drizzly. 17. Cloudy. 18. Overcast: heavy thunder showers. 19. 
Cloudy and windy. 20. Cloudy: boisterous with rain at night. 21. 
Cloudy and windy. 22. Showery. 23,24. Very fine. 25. Fine; heavy 
rain. 26. Hazy : rain. 27. Overcast and fine. 28. Slight showers : 
very fine. 29. Fine : heavy rain. 30. Fine : rain. 

Boston. — June 1. Rain. 2. Fine. 3. Fine : rain a.m. 4. Fine : rain, 
thunder, and lightning a.m. 5. Fine : heavy rain and hail, with thunder 
and lightning p.m. 6. Cloudy. 7. Cloudy : rain p.m. 8, 9. Fine. 10. 
Cloudy. 11. Rain. 12. Fine. 13. Rain early a.m. 14. Cloudy. 15. 
Fine: rain p.m. 16. Fine. 17. Fine: rain early a.m. 18. Fine. 19. 
Cloudy: heavy rain early a.m. 20. Rain. 21,22. Cloudy. 23 — 25. 
Fine. 26. Cloudy : rain a.m. and p.m. 27. Cloudy : rain p.m. 28. 
Fine. 29. Cloudy : rain early a.m. 30. Fine : rain p.m. 



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THE 

LONDON AND EDINBURGH 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



SEPTEMBER 1838. 



XXII. Discussio7i of M. Fechner's Views of the Theory of 
Galvanism, "iSoith reference, particularly, to a circuit including 
Two Electrolytes, and to the relations of Inactive Iron. By 

Prof. SCHCENBEIN. 

To the Editors of the Philosophical Magazine and Journal. 
Gentlemen, 
T N the letter I had the honour of addressing to you some 
^ months ago, I mentioned en passant that the chemical 
theory of galvanism was about to be severely attacked by 
some German philosophers. I now perceive by the 12th 
number of PoggendorlTs Annalen for 1837, that M. Fech- 
ner has laid before the scientific public his objections to this 
theory, in a paper entitled " Justification of the Voltaic 
Theory."'* Having many reasons to suspect that the contro- 
versy respecting the source of voltaic electricity will before 
long be resumed with more ardour than ever, and being be- 
sides almost sure that the results of my late researches re- 
garding the voltaic action of metallic peroxides will be made 
use of as a piece of evidence in favour of Volta's views, I 
think it not quite unseasonable to offer a remark or two upon 
some of the objections brought forward by M. Fechner. As to 
the assertions made by that philosopher with regard to some 
fundamental experiments of De la Rive, I do not feel my- 
self called upon to refute them, as no doubt the distinguished 
electrician of Geneva is himself best able to maintain the 
points attacked. The remarks I am going to make will prin- 
cipally bear upon the conclusions which have been drawn by 
M. Fechner from the results of the following experiment. 

* We commence in the present number, p. 205, a translation of M. 
Fechner's paper here mentioned. 

Phil. Mag. S. 3. Vol. V6. No. SI. Sept. 1838. M 



162 Prof. Schoenbein's Discussion ofM. Fechner's 

Ten pairs of zinc and copper, in every respect as equal to 
one another as possible, were arranged into a " couronne des 
tasses," so that half of the said pairs produced a current op- 
posite in its direction to that which was originated by the 
other half. The exciting fluid used was common water. Such 
an arrangement being connected with the galvanometer, can, 
according to either of the two principal theories of galvanism, 
have no effect upon the needle, provided everything in the 
two systems of cells be equal. Fechner, after having ob- 
tained current equiUbrium in the manner described, put mu- 
riatic acid into one of the above-mentioned systems, and found 
that in these circumstances the previous equilibrium was in 
the first instance maintained, but that by degrees the current 
of the water-cells got the ascendency over that of the acid 
system. Fechner thinks these results to be quite irrecon- 
cilable to Faraday's theoretical views on galvanism, and is 
inclined to consider his experiment as an " experimentMrn 
crucis" against the very first principle of the chemical theory 
of the voltaic phaenomena. Before judging of the validity of 
Fechner's conclusions, I must not omit to give an account of 
some of the results which I lately obtained from a great many 
experiments made upon the subject under discussion. 

1. Ten equal pairs consisting of zinc and copper were ar- 
ranged in the manner before mentioned, and the vessels hold- 
ing the former charged with common water. On closing the 
circuit by the means of a most delicate galvanometer (pro- 
vided with 2000 coils), the needle deviated a little, but after 
a very short time it returned to zero. Current equilibrium 
being thus obtained, it was disturbed again by breaking and 
re-establishing the circuit through the means of any pair of 
either system. The deviation of the needle amounted to 
about 20°, and was always such as to indicate the superiority 
of that current which was produced by the set of pairs left 
untouched. The equilibrium, however, was also in this case 
very soon re-established after the closing of the circuit. 

2. Equilibrium taking place in the arrangement just de- 
scribed, 1 added ^^^ of common sulphuric acid to the water of 
one set of the cells. On closing the circuit by means of the 
galvanometer, the needle of the instrument was made to de- 
viate about 180° in such a direction as to show the ascend- 
ency of the current excited by the acidulated water. Leaving 
the circuit closed for a few minutes, the needle however took 
up its usual position. Opening and closing the arrangement 
again by the means of any pair of plates belonging to the cells 
charged with the acid fluid, or doing the same by the means 
of the platina ends of the galvanometer-wire, had not the least 



Vieisosqfthe Theory of Galvanism. 163 

effect upon the needle; but on removing any pair of the water- 
cells from the circuit and replacing them there, the equili- 
brium was disturbed in favour of the acid system. But what 
seems to me to be still more remarkable, is the fact, that the 
same effect, only on a smaller scale, was obtained by making 
any pair belonging to the water system alternately rise and 
sink a little without removing it entirely from the circuit. 
Another fact worthy of being stated is, that immediately after 
the equilibrium had been disturbed, opening and closing 
the circuit by the galvanometer, or by any pair of the acid 
system, causes a similar effect, that is to say, a perceptible in- 
crease of the acid current. The arrangement left to itself 
closed regains, however, its previous condition within a very 
short space of time, i. e. assumes such a state of current equi- 
librium as can only be changed again by breaking and re- 
establishing the circuit by a pair belonging to the water system. 
It is also worthy of remark, that the magnitude of the differ- 
ences of currents obtained by the means mentioned is variable. 
I have repeated the same experiment over and over again, and 
at each time I got a fresh result as to the number of degrees 
of the needle's deviation ; sometimes even, no deviation at all 
took place. On making use of an aqueous acid fluid con- 
taining 1 part of sulphuric acid in one system of the cells, 
whilst there was common water in the other, I obtained a 
deviation in favour of the acid current which amounted to 
about 90° : in a very short time the needle, however, returned 
to zero. A fluid containing li, 2, 2i, 3, 3|, 4, 4i, 5 parts 
of acid did not affect the needle ; from 5^ — 8 parts produced a 
temporary deviation of about 40° in favour of the water cur- 
rent ; from 9 — 1 1 parts had no effect ; 1 5 parts caused a consi- 
derable deviation in favour of the acid current, but lasted only 
for a few moments ; 20 parts caused no effect upon the needle. 
3. A liquid containing for 100 parts of water 1 — 10 parts 
of common muriatic acid, and used in one system of the cells, 
did not cau-e any deviation; 15 parts caused a deviation of 
the needle of 40° in favour of the water current : after a short 
time the former returned to zero, but was again made to de- 
viate in the same manner as it was at first. This change of 
equilibrium into difference of currents, and vice versa, took 
place several times. From 20 — 25 parts of acid caused a devia- 
tion of about 45° in favour of the water current, which lasted 
rather a long time ; 30 parts of acid made the needle turn 
round its central point several times in such a direction as to 
indicate the prevalence of the water current. The same ex- 
periment made another time showed no difference of cur- 
rents, the needle remaining at zero. 

M 2 



164< Prof. Schoenbein's Discussion q/M. Fechner's 

4. Water containing for 100 parts 5—20 parts of com- 
mon nitric acid did not disturb the needle at all ; 25 parts 
produced a rather long continuing deviation of about 50° in 
favour of the water current; '30 parts had the same effect, 
though the difference of currents was a little smaller. If in 
the latter experiment the two systems of pairs were made to 
change their cells, so that the set of pairs having previously 
been in water were placed in the acid-cells, and vice versd^ 
a current equilibrium was obtained. In most of the fore- 
mentioned cases, where the needle remained at rest, the pairs 
of the water-cells could have their place supplied by platina 
wires, without thereby disturbing the equilibrium ; and even if 
a deviation of the needle took place (immediately after having 
effected such a change), it was always very insignificant, and 
the equilibrium of currents was speedily re-established. 

From the results of the experiments described, it appears 
that only in a few instances the chemical difference of the ex- 
citing fluids contained in the two systems of cells determines 
a difference of currents produced by the two sets of pairs, and 
that the general rule is the production of current equilibrium. 

Now, if I have correctly understood Fechner's statements, 
they imply the assertion, that on using water in one system 
and an acid liquid in the other system of cells as exciting 
fluids, and everything else being equal in the arrangement, 
the equilibrium which takes place in the first instance is al- 
ways by degrees disturbed in favour of the water current. 
If such were the case, the fact, as it seems to me, would be 
entirely contradictory to the theory of Volta ; for according 
to the views of this philosopher the current produced by the 
one set of pairs must be equal to that which is excited by 
the other set, and the addition of acid to one system of cells 
has no other effect than to increase the conducting power of 
the whole arrangement. I have already remarked, that in 
the circumstances mentioned current equilibrium is the rule, 
the contrary an exception to it, and that even if a difference 
of currents occurs, it is generally so insignificant as to be 
made only perceptible by the means of a most delicate gal- 
vanometer. We may therefore consider the facts to be in 
perfect accordance with the theory of Volta. But does not 
the current equilibrium in question disagree with that theory 
which makes the production of current electricity dependent 
upon chemical action, and the quantity of the former upon 
the extent of the latter? I think it does not, and hope to be 
able to prove the correctness of my assertion by what I am 
about to say. 

On the first view of the case, it seems, indeed, as if the fact 



Views of the Theory of Galvanism. 165 

under discussion were not at all favourable to the chemical 
theory, for undoubtedly the chemical action which takes place 
in the acid cells is, as to extent [intensity?], infinitely superior to 
that which is going on in the water cells. There should, there- 
fore, be a difference of currents proportionate to the difiference 
of the extent of the chemical actions taking place in the two 
systems. Certainly, if we do not take into account the dif- 
ferent degree of resistance which is offered to the circulation 
of the currents by the'two sets of cells, the equilibrium in 
question must appear entirely at variance with the principles 
of the chemical theory, and speak in favour of Volta's hypo- 
thesis; but by duly appreciating the circumstance alluded 
to, the theoretical difficulty and the anomalous character of 
the fact can easily be removed. 

According to the theory of the voltaic pile, such as it was 
established some time ago by M. De la Rive, the electricities 
which are set free by chemical action at the two ends of a 
closed compound circle unite themselves by two ways ; one of 
which is the pile itself, the other the conductor placed be- 
tween the poles. The quantities of the electricities recom- 
bining within each of the two conducting mediums depend, 
according to the same theory, upon the peculiar degree of the 
conducting power of each medium. Now let us at first con- 
sider only the acid cells as originating a current, and those 
charged with water merely as a medium put between the 
poles. It is manifest, that under such circumstances, by far 
the larger portion of electricities being developed by the pile, 
must reunite within the latter, and only a small quantity will 
consequently pass through the galvanometer and the water 
cells. If, as above stated, the latter are connected with one 
another by the means of platina, no current whatever circu- 
lates through the galvanometer, however violent chemical ac- 
tion may be within the water cells; but if pieces of copper or 
of any other readily oxidable metal are made use of instead of 
platina, there will pass a weak current from the acid system 
into that of water. This result is easily accounted for by the 
well-known fact, that those metals offer much less resistance 
to a current than platina does. From such being the case, it 
follows, that we should always obtain a current of the descrip- 
tion mentioned, if the pairs of zinc and copper, by means of 
which the water cells of our arrangement are connected with 
one another, only acted the part of conductors. We know, how- 
ever, that they also give rise to a weak current, which current, 
on account of the peculiarity of the arrangement, must be, as 
to direction, opposite to that excited by the acid cells. From 
the fact that in most cases above stated equilibrium takes 



166 Prof. Schoenbein's Discussion ofM. Fechner's 

place, we must infer that both currents in question are ge- 
nerally equal to one another. The equality of the currents 
resulting from our two systems of cells is, no doubt, in some 
way or other connected with the fact, that two piles containing 
the same number of equal pairs, but being charged with dif- 
ferent exciting fluids, exhibit in general no difference of ten- 
sion at their insulated poles. As De la Rive has already dis- 
cussed that point in his memoir entitled " Recherches stir la 
Cause de I'Electrzciie volta'ique,^^ I do not think it necessary 
to enlarge upon it any further. 

It appears to me that the preceding remarks are sufficient to 
demonstrate that the current equilibrium which results from 
the peculiar arrangement which has been mentioned of two 
compound circles (only differing from each other with regard 
to their respective exciting fluids) is by no means contradictory 
to the principles of the chemical theory, no more than, for 
instance, the fact is, that a pile consisting of ten voltaic pairs, 
half of them put into water cells, the other half into acid 
ones, and arranged in the usual way, produces a current much 
weaker than that which is obtained from five pairs alone 
placed within the acid fluid. For the same reasons which 
make Fechner consider the equilibrium in the first case as an 
evidence against the correctness of the chemical theory, he 
must draw similar conclusions from the results of the second 
case; for he may ask, why should the voltaic effect of ten 
pairs be smaller than that produced by only five pairs ? as 
there can be no doubt that the extent of the chemical action 
of the whole arrangement is greater than that of only a part 
of it. After what has already been said about the subject, it 
would be quite superfluous to answer such a question. 

As to the differences of currents mentioned in the beginning 
of this paper, those differences being sometimes in favour of 
the water system, sometimes of that of the acid system, I am 
inclined to think them connected with certain changes which 
the pairs functioning in the pile undergo with regard to their 
conducting powei , though I am not able as yet to assign the 
ultimate cause of the modifications in question. There can, 
however, hardly be entertained a doubt about the occurrence 
of such changes ; and to prove the correctness of the assertion, 
I have only to mention iron, which being in its peculiar con- 
dition, proves to be a very bad current-conductor, compared 
to what it is in this respect when in its ordinary state. 

Dr. Faraday, in his comments upon my first letter addressed 
to him, (L. & E. Phil. Mag., vol. ix. p. 60.) says that the voltaic 
relation of inactive iron to platina afforded a decisive proof, 
that contact of itself, independent of chemical action, is inca- 



Views of the Theory of Galvanism, 167 

pable of producing current-electricity. I myself have drawn 
a similar conclusion from a series of facts, which I made known 
through the Phil. Mag. some time ago. 

Fechner now asserts that the phaenomena alluded to do 
not prove the least thing in favour of the chemical theory. 
Although the results of my late researches have, indeed, shown 
(see L.&E. Phil. Mag., No. 74, 1838,) that inactive iron, being 
voltaically associated with platina and put into nitric acid, pro- 
duces a weak current, which, as it seems, is quite independent 
of any chemical action, I nevertheless maintain that Faraday 
and myself were fully entitled to draw the inference mentioned. 
Hereafter I shall give my reasons for doing so. In support of 
his sweeping assertion, Fechner says that he and Wetzlar had 
satisfactorily proved, that the modification which iron under- 
goes in nitric acid renders that metal more negative than it is 
in its natural state. The fact that a highly negative metal 
neither precipitated copper from a solution of blue vitriol, nor 
was affected by nitric acid, nor produced a perceptible current 
when voltaically combined with platina, could not therefore 
be considered as irreconcilable with Volta's theory, &c. With 
all deference to M. Fechner's great abilities and merits as a 
philosopher, and particularly as an electrician, I cannot make 
up my mind, as already stated, to submit myself to his judge- 
ment. As to Mr. Faraday, I do not know whether he is pre- 
pared to acknowledge the fallacy of his reasonings, but I 
strongly doubt [whether] he is. The reasons which determine 
me to insist upon my former opinions are as follows. 

The assertion of M. Fechner, according to which iron, by 
assuming its peculiar condition, becomes a highly negative 
body, has, if translated into the language of the chemical 
theory, no other meaning than this ; — that iron becomes a metal 
less oxidable than it is in its natural state. Fechner's view 
of the case implies to a certain degree a hypothetical expla- 
nation of the non-oxidability of iron, whilst I confine myself 
to stating facts, and the order in which certain phaenomena 
succeed to one another. But let us for a moment grant the 
existence of electrical relations of bodies to one another, such 
as supposed by the voltaists; and if we further admit that by 
some means or other, for instance, by a peculiar action of 
nitric acid, iron can be changed from an electro-positive metal 
into a negative one, it is to be asked why such a change is ef- 
fected by making common iron the anode of a current. Ac- 
cording to my experiments, iron, whilst acting the part of the 
positive electrode of a pile, does not throw down the smallest 
particle of copper out of a solution of blue vitriol, and allows 
oxygen to be disengaged just as platina does. Agreeably 



168 Prof. Schojnbein's Discussion of M. Fechner's 

to the same experiments, the circulation of the current has no 
sooner been interrupted than the iron is acted upon by the 
copper solution in the usual manner. On using any other 
aqueous solution of oxi-acids or oxi-salts, which in ordinary 
circumstances act chemically upon iron, we obtain the same re- 
sults. Now in accordance with his views, Fechner is forced to 
admit, in order to account for the inactivity of the metal, that 
iron by acting as the positive pole of a pile is rendered an elec- 
tro-negative body. I must confess it appears utterly impossible 
for me to conceive how the admission of such a state of things 
can be reconciled to the principles of Volta's theory, and the 
electro-chemical systems of our days. According to my hum- 
ble opinion, the very reverse of what is really the case should 
take place, that is to say, iron performing the function of the 
positive pole of a pile, ought to become a metal more positive, 
or what comes to the same, more oxidable than it is in its 
usual condition. Is it possible that the same particles of a 
body are at the same time in two opposite electrical states, or 
can any substance at the same time attract and repel oxy- 
gen? It is quite obvious that Fechner's assertion implies the 
admission of such a state of things ; for the disengagement of 
oxygen from the iron must be considered, according to his 
views, as the effect produced by two different causes : first by 
that metal being the positive electrode, and then by its (the 
iron) being a highly electro-negative body. For my part, I 
cannot adopt such an extraordinary opinion, and must conse- 
quently consider as erroneous Fechner's assertion, according 
to which the peculiar condition of iron depends upon the me- 
tal having changed what is called its natural electro-chemical 
relations. 

I certainly do not pretend to know in what manner a cur- 
rent changes the natural qualities of iron ; but my ignorance 
on this point does not force upon me a hypothesis so ill suited 
to the principles of the chemical theory as the one spoken of 
appears to be, with regard to the voltaic-electro-chemical sy- 
stem which is maintained by Fechner. 

Before passing to another subject, I have still a remark or 
two to make respecting the matter in question. If a piece of 
copper (in the shape of a wire,) and one of inactive iron are 
connected on the one side with a galvanometer, and on the 
other with a solution of blue vitriol, the needle will be made 
to deviate in such a direction as to indicate a current passing 
from the copper through the fluid into the iron. Such a state 
of things lasts, however, only for a few seconds, the current 
quickly changing its direction, and the iron becoming positive 
with regard to copper. This change occurs at the very same 



Views of the Theory of Galvanism. 169 

moment when the former metal ceases to be in its peculiar 
state. Similar phaenomena take place, if in the experiment, 
instead of a solution of copper, nitric acid (not too strong) is 
made use of; but no such results' are obtained, when, in place 
of copper, a metal is substituted which is not chemically acted 
upon by the fluids mentioned. It is certainly true, that inact- 
ive iron being put into a copper solution becomes of itself act- 
ive ; but if the peculiar condition of the metal has been called 
forth by repeated immersions in nitric acid of I '35, by which 
means the highest degree of stability of chemical inactivity is 
excited, it can stand rather a considerable length of time 
in such a solution before it becomes active ; whilst, as already 
stated, the peculiar condition of iron is almost instantaneously 
destroyed, if the metal be voltaically associated with copper or 
any other of the more readily oxidable metallic substances. 
It is hardly necessary to mention here, that copper is che- 
mically acted upon by solutions of the deut-salts of that 
metal. Now if, according to M. Fechner's opinion, inactive 
iron be a negative metal, how does it happen that in the cir- 
cumstances mentioned, the iron changes so suddenly its vol- 
taic character and turns positive again; and how comes it 
that this change of state takes place only in case the metal, 
which is voltaically combined with the iron, acts chemically 
upon the fluid into which both metallic substances are plun- 
ging ? I account for the change in question in the following 
manner. My experiments have proved, that inactive iron by 
being made the cathode of a current of a certain strength 
loses its peculiar state, i. e. turns active. Now if such inact- 
ive iron be voltaically associated with copper for instance, 
and both metals put into a solution of blue vitriol, the copper 
will be oxidized, and by this means a current excited to which 
the iron of the arrangement bears the relation of the cathode. 
This current must, according to what I said before, destroy 
the peculiar condition of the latter metal and throw it into 
chemical action. This action being superior to that which 
takes place at the copper, the current produced by the for- 
mer must also surpass in strength the current which is ex- 
cited by the latter action ; and hence it follows that iron must 
become positive with regard to copper. 

As Fechner does not allow chemical action to be a source 
of current electricity, he of course cannot take the least notice 
of what is going on in the voltaic arrangement described in a 
chemical respect, and he must find out some other cause in 
order to account for the change of the voltaic relations of 
both metals to one another. What this cause may be, I must 
confess I have not the least idea of. 

There is another fact that bears upon our question and 



1 70 Prof. Schoenbein on the Theory of Gahanism. 

about which I must offer some remarks. If two pieces of iron 
wire, one of which is to be inactive, the other in its natural con- 
dition, are connected with a galvanometer, and the free end 
of the former first put into common nitric acid, and afterwards 
the free end of the oi'dinary wire, it is well known from my 
former experiments that the latter piece of wire becomes in- 
active, and that at the same time a current is produced which 
passes from that wire through the acid into the inactive one. 
The latter wire, therefore, is to the common one as platina is 
to zinc. Such a state of things, however, lasts only for a few 
moments, the voltaic difference of the two iron pieces disap- 
pearing very quickly. If in the experiment described the or- 
dinary iron wire be first plunged into the acid, the inactive 
one is thrown into chemical action, and a current excited, to 
which the latter wire acts the part of the cathode ; but no 
sooner has the passive iron been rendered active, than the cur- 
rent ceases, or rather current-equilibrium is established. Now 
if chemical action has nothing to do with the production of cur- 
rent electricity, why does the order in which our wires are 
plunged into the acid determine the results spoken of? Ac- 
cording to Fechner's views, inactive iron ought to remain in 
its peculiar condition, whether it be put before or after the 
ordinary wire into the fluid ; and the more should this be the 
case, that the Saxon philosopher does not seem to admit of the 
existence of any causal connexion between a current and the 
inactivity of iron, making the latter depend upon a peculiar 
action of nitric acid or nitrate of silver on that metal. I 
scarcely need to mention, that the same principle made use of 
to account for the phaenomena to which iron associated with 
copper gives rise in a solution of blue vitriol, is perfectly ap- 
plicable to the facts just now stated ; and I should think that, 
according to the present state of science, no other account of 
them can be given. In the experiments described, chemical 
actions and voltaic effects appear, indeed, so closely connected 
with one another, that an unbiassed mind can hardly help 
considering the first as the cause of the latter. 

I have perhaps enlarged too much upon my subject, and am 
really afraid of being chargeable with prolixity ; but as the dis- 
cussion into which I have entered regards the very first prin- 
ciple of the chemical theory of galvanism, I thought I could 
render some service to science by minutely appreciating the 
value of the objections which have been brought forward 
with the view of invalidating or rather overthrowing the che- 
mical theory. 

Up to this present moment I have considered the definite 
action of an electric current, and the fact, that the quantity of 
the latter produced by an hydro-electric arrangement is deter- 



Mr. C. Binks on Voltaic Electricity. 171 

mined by the quantity of metal oxidized, as the most conclu- 
sive proof of the dependence of current electricity upon che- 
mical action ; but to my great surprise, I am now given to 
understand that those important facts do not prove anything 
at all in favour of the chemical theory, though I have not yet 
been so happy as to meet with even the slightest attempt to 
explain them according to the principles of Volta's hypo- 
thesis. Certainly, if Faraday's beautiful discovery is rejected 
as an evidence, we must despair of finding out another of 
more weight ; and I am afraid any further discussion upon the 
subject with our antagonists will prove perfectly useless and 
a mere waste of time on our part. 

I am, gentlemen, yours, &c. 
Bale, 14th June, 1838. C. F. ScHCENBElN. 

XXIII. On some of the Phcenomena and Laws of Action of 
Voltaic 'Electricity, and on the Construction of Voltaic Bat- 
teries, S^c. By Christopher Binks. A Second Communi- 
cation, addressed to J. F. Daniell, Esq., F.R.S., S^c., Professor 
of Chemistry in King's College, London. Part the First*. 
[Continued from p. 145.] 
Section VI. 
T^O determine the comparative amount of voltaic action in- 
■*- duced in any single arrangement under different distances 
of the two elementary plates from one another, continued. 

115. The preceding part of the inquiry relates to the in- 
fluence exercised by distance upon a voltaic arrangement, in 
which the elementary plates are of an equal size relatively ; 
and it has been shown (84 to 92) that of whatever magnitude 
the couple itself may be, so long as its two plates are equal in 
size one to the other, the influence of distance is the same as 
has been stated in the preceding section. 

116. It is now required to find the comparative effects of 
distance in any arrangement, when the elementary plates are 
of an unequal size relatively, but whilst all other conditions 
of the experiment remain the same as before. 

117. The elementary plates may differ from one another in 
size to any extent : the zinc plate may be a small one, and the 
copper plate be made the larger, and that to an unlimited ex- 
tent ; or, on the other hand, the copper plate may be made the 
smaller of the two, and the zinc one be increased in size to an 
unlimited extent. 

» This portion of Mr. Binks's Second Cpminunication was by mistake 
termed Part the Second in our last, 



172 Mr. C. Binks on Electricity^ 

118. But in the instances that immediately follow, the ex- 
periments will be restricted to that condition of the arrange- 
ment in which the zinc plate is the smaller of the two. 

119. The plates used in the preceding experiments were 
each one inch square (93); but one side of the zinc being co- 
vered with wax, was not brought into action, whilst both sides 
of the copper plate were exposed to the action of the acid 
throughout: the total area of the zinc surface was therefore 
equal to one square inch, and that of the copper to two square 
inches. 

120. The experiments to determine the further effects of 
distance are now to be varied by the use of larger copper 
plates, whilst the magnitude of the zinc plate remains precisely 
the same as before. 

121. The set of copper plates prepared for these and the 
subsequent experiments amounts in number to 13, beginning 
from the size of 2 square inches of total surface, as in the one 
above, and progressively increasing by the following rate : — 

122. Total superficial area in square inches of each copper 
plate. 

2. 4. 8. 12. 18. 24. 32. 40. 50. 60. 72. 98. 128. 

123. Each plate was attached to a wire 5 feet in length, in 
the same manner as before. The various precautions used in 
preparing this set of plates, and in adapting them to their 
present use, have already been fully explained (62). 

124. Now the immediate object of the inquiry is to ascer- 
tain what influence is exercised by distance upon any arrange- 
ment which may be composed of a zinc plate having a total 
superficial area of 1 square inch, and of a copper plate whose 
area is any of those just stated (122). The relative distances 
contemplated range between \ of an inch and 48 inches ; and 
to complete the investigation, the acid mixture should be va- 
ried in strength in the four different degrees used in the for- 
mer experiments. 

125. A little consideration will show how innumerable and 
varied the experiments would need to be, in order to com- 
plete an investigation which should undertake to determine 
the effects of distance under all the varied changes of the con- 
ditions of such arrangements of which they are capable. 

126. But it will perhaps be unnecessary to pursue the in- 
vestigation to so great a length. Such results as it may be 
desirable to seek for will perhaps be obtained by a very few 
observations comparatively ; and as most likely to contribute 
to this abridgement, the order of the experiments as they now 
follow was determined upon. 

127. The amount of action yielded by any voltaic arrange- 



Voltaic Batteries^ S^c. 173 

ment will be increased by increasing the size of either plate 
of the couple employed ; but the extent to which this increase 
in amount of action can be carried is limited. The rate in 
which this increase proceeds, and the influence upon that rate 
by the different conditions of strength of acid mixture, and 
relative distances of the plates, together with some other at- 
tendant phaenomena, are examined in a succeeding section. 
My present purpose is to state the fact of this increase, and 
not to determine either its rate or its extent. 

128. In the investigation now on hand, the amount of vol- 
taic action obtained by a small couple of the same magnitude 
as those used in the last section, and having its plates at the 
relative distance of ^ of an inch, is used as a standard of com- 
parison. 

129. The amount of action given by this couple being de- 
termined at this first position, in an acid mixture of uniform 
strength and dimensions, its copper plate is then removed to 
other and greater distances from the zinc, and the amounts 
given at those positions likewise determined. But the rate 
at which the amount decreases upon this increase in distance 
has already been determined by the experiments in the last 
section. 

1 30. It is now proposed at these several distances, to in- 
crease the size of the copper plates till the amount of action 
obtained shall become equal to that yielded by the standard 
couple at the first or standard position ; the immediate object 
being to determine the relation between the sizes of the plates 
required to produce this amount, and the distances at which 
they are required. 

131. By way of illustration, let the distance to which the 
small copper plate is removed from the zinc be supposed to 
be 24 inches ; and that the amount of action yielded there is 
(as under some conditions is the fact,) about three times less 
than that obtained at the first or standard position. Then by 
substituting larger copper plates in succession in the place of 
the small one, let it be determined by what size the amount 
becomes three times greater, or exactly equal to that given 
by the small plate at the first distance of ^ of an inch. 

132. But it is not yet proved that any addition whatever to 
the size of the copper plate, at the supposed position of 24 inch- 
es, will give an amount of action three times greater, or an 
amount equal to that required. 

133. Before proceeding by an appeal to experiment to de- 
termine this point, it might be presumed that each successive 
addition to the size of the copper plate, whether at 24< inches 
distance, or at whatever other position the trial might be made, 



1 74 Mr. C. Binks on Electricitt/, 

would be followed by a corresponding increase in the action 
of the whole arrangement; and it might be presumed also, 
that inasmuch as the amount of action given by the standard 
plate is reduced from 3 to 1 by the removal from ^ of an inch 
to 24 inches, but to a less extent in the intermediate positions, 
it would require a larger plate at 24 inches to restore the stand- 
ard amount than at any of the intermediate positions, or in 
other words, that a copper plate progressively smaller would 
be required to restore that amount as we progressively ad- 
vance to positions nearer to the zinc or standard position. 

134. It will be of some advantage at this stage, before pro- 
ceeding on to the more specific details, to give a general out- 
line of the kind of results which have been obtained by the 
experiments entered upon to determine the points just sug- 
gested ; only premising that the numbers and positions now 
used must be considered as illustrative merely, and not as 
actual representations of any one particular instance of the 
general phaenomena and relations which have been thus de- 
tected; the whole of which, it will be found subsequently, are 
influenced by a variety of circumstances which could scarcely 
have been anticipated, and which it becomes the particular 
business of the inquiry to detect and estimate as it proceeds. 

This general illustration is given in the hope that it may 
serve to simplify and more clearly define the nature of the 
somewhat complicated examinations upon which I am now 
entering, the precise numerical results of which are immedi- 
ately to follow. 

1 35. Let it be supposed that the trials are made in a mass 
of liquid contained in an oblong-shaped trough, similar to 
that used in the experiments of the last section. 

136. Let the amount of action given at the distance of ^ of 
an inch by small standard plates be supposed equal to 3, 
and that obtained at 24 inches off equal to 1 ; then, whilst at 
the latter position, let the small copper plate be removed, and 
others progressively larger be substituted for it in succession ; 
and it will be found that by no increase whatever to the size 
of the copper plate, can the same amount of action be obtained 
at 24 inches, that was found by the small plate at the first or 
standard position. A certain increase in amount will be ob- 
tained, perhaps equal to 2, but in no case to 3, the amount 
required. 

But let the same trials be now repeated at other positions 
nearer to the fixed zinc plate, say at the several positions 
reached by successive steps of 2 inches each, when the follow- 
ing unexpected results will be presented: — It will be found 
that neither can the required amount, 3, be obtained at any of 



Voltaic Batteries^ Sfc. 175 

the several positions intermediate between the distance of 24 
inches and 12 from the zinc, but that at 12 inches a certain- 
sized plate will give the amount sought for. 

Proceeding on in the same manner still nearer to the zinc, 
the required amount will be obtained likewise at 10 inches and 
at 8, but only by plates larger than that yielding the same 
amount at 12; but at the distance of 6 inches again, as at 24, 
it cannot be obtained by any sized plate that the dimensions 
of the trough will allow to be tried; whilst at the remaining 
successive positions between 6 inches and the zinc or stand- 
sivd position, the required amount will be readily obtained by 
plates gradually diminishing in size, as the positions approach 
nearer to the zinc, till we again reach the first position of \ of 
an inch, and consequently obtain the amount by a plate equal 
in size to that first employed. 

137. I proceed now to the details of the experiments by 
which these and the remaining results have been detected ; 
and it will be borne in mind, that it is the relation between 
the magnitudes of the two copper-plates — the standard and 
the required plates — those by which the equal amount of 
action is given, and the distances at which they are respect- 
ively required, which is the result immediately sought for. 

1 38. As a specific example of this kind of investigation, I 
select the following average instance, the details of which 
being given separately, will contribute to the better apprehen- 
sion of the kind of results which are to be more fully embodied 
in the succeeding tables. 

139. The small standard couple, with its copper plate at the 
relative distance of |- of an inch from the zinc, gives the usual 
measure of j—th of a cubic inch of hydrogen in 85 seconds; but 
removed to the distance of 10 inches, the time required is 160 
seconds. Then, in the place of the smaller copper plate, and 
at the distance of 10 inches, are substituted other copper plates 
in succession, and progressively larger, when the time in which 
each yields the measure of hydrogen is as follows. 

Table (No. 7). 
At ^ inch At 10 inches distance, 

distance. 
Total surface in"| 
square inches of \- 2. 2. 4. 8. 12. 18. 24. 32. 40. 

each copper-plate.J 
Time in seconds ^ 
in which each yields 
the equal measure 
of hydrogen. ^ 

140. Now it will be remembered always, that the fewer the 



85' 



160" 120" 1 10" 90" 85" 80" 



1 76 Mr. C. Binks on Electricity^ 

number of seconds required for the production of the measure 
of gas, the greater is the amount of voltaic action. In this in- 
stance we perceive that the amount is reduced from 85" to 
160" by the removal from^ of an inch to 10 inches, and then 
at the latter distance, that the amount is again gradually in- 
creased by each addition to the size of the copper plate, till 
it again reaches to 85". It is still further increased by a 
further addition to the size of the plate; but I here purposely 
avoid carrying out the numbers beyond the one immediately 
sought for, namely, the required number, in this instance 85". 
So soon as that amount is given, I cease to register any 
further results obtained at that particular position ; for were 
the results pursued beyond this point, we should then be in- 
troduced to another series of changes, the consideration of 
which must be reserved for another section. 

141. But besides that at some distances the action, by this 
addition to the plate, increases to and beyond the amount re- 
quired, at others it never reaches that amount ; and when the 
latter is the case, the trials by the larger plates are carried fully 
out to discover the number and the size making the nearest 
approach to the one required. And both the required num- 
ber, when that is obtained, and where not obtained, that ma- 
king the closest approach to it in amount, are distinguished 
by asterisks throughout the tables following. 

142. Now it is seen in this example, that the standard or 
required amount 85" is obtained (when the plates are 10 inch- 
es apart,) by a copper plate having a total area of 18 square 
inches, whilst the same amount is given (at the distance of \ 
of an inch,) by one whose total area is only 2 square inches. 
It requires therefore, in this instance, that the copper plate of 
any couple should be nine times larger to produce at the di- 
stance of 10 inches, the same amount of action which is pro- 
duced at I- of an inch. But this example gives the amount 
obtained for one position only, and under only one general 
condition of the whole arrangement, though the conditions 
under which the arrangement may be placed are various. 

143. The first of the succeeding tables will contain the re- 
sults obtained by testing the operations of an arrangement in 
this manner at each position, within the range of 12 inches 
from the zinc, whilst all its attendant conditions remain uni- 
form ; and such results being obtained fully for any one case, 
it is then required to find whether, if the acid mixture be al- 
tered in strength, these results will be altered likewise — in 
what manner and to what extent; and also, if possible, to 
discover whether there be any other causes influencing the 
operations of such arrangements than those originating in 



Voltaic Batteries, S^c. 



177 



the strength or density of the acid mixture, in the relative di- 
stances, and the relative dimensions of the two plates. 

144. In accordance with this design, the second table will 
show the results of a like series of observations to the first, 
but made under a change in one of the conditions of the ge- 
neral arrangement, viz. in the strength of the acid mixture ; 
whilst all other conditions remain the same as before. 

Table (No. 8). 

1 45. Showing the total superficial areas, in square inches, of 
the copper-plates ; and the time, in seconds, in which each j'ields 
the jjjth of a cubic inch of hydrogen at the different distances. 

Area of zinc plate 1 square inch, specific gravity of acid 
mixture 1*013, the depth 6 inches. Trough the same as be- 
fore. Temperature 55° F. 



Dimensions of] 


the copper-plates }. 2 4 8 12 18 24 32 40 50 60 72 


in square inches 


•J 1 


S S ' 


i 


-c 


*170" 






















-a 2 


1 


235 


*170 




















(3 

- h <o 


2 


© 


365 


280 


230" 


205" 


*I70" 






n 






II 


•-H art 


4 
' 6 


o 


^ 360 
^ 356 


300 


270 


225 


215 


*205" 


270" 


245 


245" 


245" 


220 




jj 


340 


335 


285 


275 


300 


450 


«270 


335 


320 


325 


S3 U O 


8 


<u 


390 


320 


300 


285 


275 


*270 


385 


345 


335 


335 


335 


to ,ri N 


10 


s 


450 


370 


335 


300 


*345 


385 


675 


460 


450 


400 


425 


'^i%. 


12 


H- 


475 


380 


335 


*300 


*300 


450 


670 


405 


450 


400 


405 



14-6. It is shown by the results contained in this table, that 
the plates of the small standard couple, on being separated 
from one another through the several relative distances of ^ 
of an inch and 1 2 inches, afford the same kind of results as 
have already been exhibited in tables Nos. 5 and 6. 

i4;7. These results are similar as regards the alternation in 
amount of action occurring at one particular position within 
that range, and in the progressive diminution of that action, 
which takes place as the distances increase from the first to 
the last position ; that amount is equal to 170" at the distance 
o{\ of an inch, and to 4'75'^ at 12 inches. These results are 
placed in the first perpendicular column of this table, under- 
neath the number 2, representing the total extent of surface 
of the copper-plate by which they are yielded. 

Its. Then, on substituting at each distance, larger copper- 
plates in succession in the place of the standard one, we have 
the results thus afforded, shown in the horizontal lines of this 
table. 

14-9. We see that at the distance of 1 inch, the standard 
amount 1 70" is obtained by a plate having a surface of 4 square 
inches, or one twice the size of that needed at a ^- of an inch ; 

Phil. Mag, S. 3. Vol. 13. No. 81. Sept. 1838. N 



178 Mr. C. Binks on Electricity , 

and that at 2 inches distance, the amount goes on increasing 
by each addition to the plate, till it reaches 170", which is 
given by a plate of 18 square inches, or one about 9 times 
larger than that needed at the first position, and 4 times larger 
than that needed at the second. 

150. But beyond these distances, the amount is not ob- 
tained by any addition to the size of the plate. At 4< inches, 
the next position, occurs the singular appearance of the great- 
est amount of action, 205", which occurs throughout the range 
of plates at that distance, being produced by a plate small in 
size compared with many employed in it. This is yielded by 
a plate of 24- square inches, whilst others larger and ranging 
between 24 and 72 square inches give a less amount. 

lol. The same phenomenon occurs at the remaining di- 
stances, but to a different extent, and by different sized plates 
in each. These particular numbers in each column, wherever 
the amount sought for is not obtained, are considered as those 
making the nearest approach to that amount ; and constituting 
as they do valuable data for future reasoning, they are those 
distinguished in the table by a star, and by the dotted lines in 
the subjoined diagram. 

Table (No. 9). 

152. The same as before in all respects, except the strength 
of the acid mixture, which is 1*090 specific gravity. 



Surface of the] 






copper-plate in > 


2 4 8 12 


18 24 32 40 50 60 72 


square inches. J 






11^1 


i 


_ ^ 


* 55" 
























I 


•^ 


100 


60" 


*55" 


















.5 ^H-P. 


2 


a 
o 


130 


80 


75 


65" 


60" 


*55" 












.a o-c 


. 4 




135 


90 


85 


70 


75 


65 


60" 


*55" 








r 6 


£- 


■ 135 


105 


90 


85 


70 


75 


75 


70 


65" 


*60" 


70" 


52S 


8 


u 


135 


95 


75 


60 


65 


*60 


75 


65 


65 


70 


75 


Dis 
of tl 

thefi 


10 


s 


150 


85 


80 


75 


75 


75 


85 


*65 


70 


70 


70 


12 


H . 


155 


100 


90 


85 


70 


*60 


75 


65 


65 


70 


70 



153. We perceive that throughout this table the same ge- 
neral phaenomena are presented as in the former one, differ- 
ing only in degree; an effect which must be attributed to the 
difference in the strength of the acid mixture, that being the 
only condition of the general arrangement in which any change 
has been made. 

154. The standard amount of action 55", is here regained 
at the 3 several positions 1, 2, and 4 inches distance ; whereas 
in the other case, it was regained only at the two first. And 
the plates so required to reproduce this standard amount are 
of a larger size comparatively, but appear to increase by a re- 
gular progression, as in the former instance. 



Voltaic Batteries^ S^c. 



179 



155. In the former case that progression is 2, 4, and 18 ; 
in the latter, 2, 8, 24, and 40. There is a sufficient degree 
of regularity in each of these rates of increase, without the ne- 
cessity of making more than a reasonable allowance for the 
imperfections of actual experiment, to indicate that the phae- 
nomena in question are guided, as in every other class of vol- 
taic action, by the influence of some fixed law, to which these 
numbers must be considered as making but a mere approxima- 
tion. 

156. Beyond the distances at which the standard amount 
is required in this table, we see, as in the former one, that a 
certain maximum amount of action is obtained in each column, 
and by different sized plates in each. At 6 inches, the next 
position, a maximum amount of 60" is given by a plate of 60 
square inches, whereas at the position following, or at 8 in- 
ches, the same amount is yielded by a plate of only 24 square 
inches, and so on ; the operations, after we have passed a par- 
ticular position, suirering a series of peculiar changes or al- 
ternations, exactly similar in their general character to those 
observed in the fifth table. 

Fig. 2. 





a 


1 


Z a 

1 






■■| 


1 


s 


C 


O' 


b 



f ! 



b 



16 



*«-« 



157. For the sake of still more clearly exhibiting the re- 
sults which I have here more particularly in view, I will transfer 
them from the table to the annexed diagram (Fig. 2), in which 
the horizontal line A B represents the length of the mass of 
liquid in which the plates are acting, being supposed to pass 
through its centre, and the perpendicular line C D its depth. 
At Z C are the standard plates at their first position, and the 
numbers 1, 2, 4,&c. on the horizontal line, show the different di- 
stances to which the copper plates are successively removed and 
tried. The plain lines passing at right angles through this ho- 
rizontal line, represent the particular copper-plates (in the ex- 
act linear measure of their squares), which at each position 
yield the required amount of action ; and the dotted lines re- 
present also the exact dimensions of those plates which yield, 
at the respective positions, the amount nearest to the one 
sought for, when that amount itself is not obtained. The 

N2 



180 Prof. Forbes's Researches on Heat. 

whole figure shows the exact relative proportions of the plates, 
the exact distances and dimensions of the mass of liquid, on a 
scale reduced from those actually employed. 

158. The lines a, «, a, represent the copper-plates found 
by the experiments contained in the first table (No. 8), and 
those marked b, b, b, the plates from the second table 
(No. 9). It is almost needless to remark, that the plates, 
though shown separately in the figure for the sake of the com- 
parison, must be considered as having occupied precisely the 
same position in actual experiment. 

[To be continued.] 

XXIV. Researches on Heat. Third Series. § 1. On the un- 
equally Polarizable Nature of different Kinds of Heat. 
§ 2. On the Depolarization of Heat. § 3. On the Refran- 
gibility of Heat. By James D. Forbes, Esq.., F.R.SS. 
Li. 4* E., Professor qf Natural Philosophy in the University 
of Edinburgh. 

[Continued from p. 113 and concluded.] 
§ 3. On the Refrangibility qf Heat. 
CINCE the admirable discovery by M. Melloni of the 
^ power of rock-salt to transmit and refract heat of every 
kind, one of the most obvious and important questions(formerly 
intractable) of which it seemed to offer the means of solution, 
was the accurate determination of the refrangibility of heat 
from various sources, luminous or non-luminous. Such a 
determination is of the first consequence to the formation of 
a just theory of heat, and a detection of the subtle bond by 
which it is connected with the comparatively familiar modifi- 
cations of light. 

Such experiments have not been wanting. M. Melloni, 
in his second memoir on radiant heat, in the Annales de Chimie 
for April 1834, has described the apparatus which he em- 
ployed, and which is figured in Plate III. of that volume*. It 
consists of a thermo-electric pile, constructed of a single ver- 
tical row of elements, so as to be exposed to a very narrow 
beam of heat. It was made to move on a sector of a circle, 
at whose centre was placed a prism, by which the beam of 
heat was refracted from its primitive direction a b into that 
cd, (see next page), and therefore produced a maximum 
effect on the galvanometer when the pile was at d. The 
other parts maintaining the same positions, it is evident that 
the pile must be moved into the position d\ if the source of 

[* A translation of Melloni's second reemoir on radiant lieat will be 
found in the Scientific Memoirs, vol. i. p. 39. — Edit.] 



Third Series. — Refrangibility of Heat. 181 

heat be now one yielding rays of greater refrangibility. Al- 
though the radius of the circular arc was (if I understand the 

p 

Fig. 1. K * 




account rightly) eleven inches, but little deviation of position 
was required for heat from different sources ; and M. Melloni 
admits that, whilst his experiment indicates the difference of 
refrangibility, it is inadequate to measure it. 

There are many reasons why such a form of apparatus 
must be rejected for accurate observations. I will mention 
only the impossibility of obtaining a beam of heat which shall 
preserve the same breadth at different distances from its source 
(of course, supposing the rays rendered as parallel as possible 
by refraction through a rock-salt lens), arising, 1. from the 
angular magnitude of the source; 2. from the scattered re- 
flection and refraction at the surfaces of the lens and prism; 
3. from the want of homogeneity of the ray. On all these ac- 
counts, the beam must have acquired a very sensible breadth 
at the distance of the pile, and consequently the effect of heat 
must be perceptible, and even nearly uniform, through a cer- 
tain space. I may also add from experience, that the diffi- 
culty of varying the arrangement of an experiment, so as to 
get a maximum heating effect at the pile, is so considerable, 
that no delicate result can be deduced from the merely ten- 
tative procedure. Finally, the smallness of the variation of 
refrangibility seems to require some more critical method of 
ascertaining its measure. On all these grounds, it seemed to 
me desirable to discover a method in some degree less open 
to objection. 

The phsenomenon of total reflection, successfully employed 
by Dr. Wollaston in the measurement of refractive indices in 
the case of light*, presents the advantage of being (theoretic- 
ally at least) abrupt in its action, the transition from partial 
to total reflection being (with the necessary exception arising 
from the want of homogeneity) an instantaneous change, 
amounting in the case of light to many times the intensity of 

* Phil. Trans. 1802. 



1 82 Prof. Forbes's Researches on Heat, 

the smaller effect. It seemed reasonable to expect, that an 
apparatus constructed on the principle of determining the 
critical angle of total reflection of heat from different sources 
within a prism, would afford much more definite information 
as to the refrangibility of heat than any other method. After 
much consideration, an apparatus of the following kind was 
adopted. 

It is fundamentally composed of a jointed frame, resembling 
a box exactly square, ten inches in the side, without top or 
bottom, and having hinges at every angle, so that it may be 
formed into a lozenge of any degree of obliquity. This is 
seen in Plate IV. fig. 1, and marked A B. By an arrange- 
ment presently to be described, the rays of heat are made to 
pass parallel to the edge a c of one of the sides of the box, 
and to fall upon the prism P, whence, after undergoing re- 
flection (total or partial) at the posterior surface of the prism, 
they proceed parallel to the line a d, and fall upon the sen- 
tient extremity of the pile at p. Now, in order that this 
course may be taken by the reflected rays, it is necessary that, 
supposing the prism to be an isosceles one, the posterior re- 
flecting surface a' Z/, fig. 2, should form equal angles with the 
incident and reflected rays c e and yd. It was to effect this 
that the arrangement of the jointed lozenge was adopted. 
The prism P (fig. 1.) rests on a column O, moveable round 
the line of junction of the sides C and D of the lozenge. The 
column O has connected with it a tail-piece of brass a E 
passing through the diagonal of the frame, and preserved con- 
stantly in that position by a slit parallel to its length, through 
which passes a clamping screw b, serving at once to maintain 
this constancy of direction, to secure the form of the move- 
able lozenge, and by means of an index pointing to a gradu- 
ated scale of inches reckoned from a, along a E, to determine 
the length of the diagonal a b at any moment, and consequently 
the angles of the lozenge. 

A little consideration of this mechanical arrangement, will 
show how it is adapted to the end in view. The rays from a 
source of heat S, rendered parallel by the lens of rock-salt L, 
fall upon the prism P, and after undergoing two refractions 
and one reflection, they fall upon the sentient surface of the 
pile p. This will always take place so long as the posterior 
surface of the prism forms equal angles with the lines ac, ad^ 
which will be secured by making it truly perpendicular to the 
tail-piece a E, by which it is guided, and which of course al- 
ways bisects the angle cad. Now, it is evident that, whilst 
the angle cad remains small, the reflection will continue 
partial^ but that as the diagonal a 6 is shortened, a point will 



Third Series,— Refrangibility of Heat, 183 

be reached when total reflection abruptly commences, which 
ought to be indicated by a saltm in the movement of the gal- 
vanometer connected with the pile. This critical angle will 
be soonest attained for rays of greatest refrangibility, and the 
calculation of the refractive index of the prism is reduced to 
a simply mathematical problem. 

The following is the problem to be solved, viz. : A ray of 
light G D (fig. 2.) falls upon the surface A C of a prisma 'which 
has the angles at A and B equal ; it falls upon the surface 
A B a/ the critical angle of total reflection; required the index 
of refraction (fx,) of the prism, the angle of incidence (a) being 
given. 

Fig. 2. 




An investigation of little difficulty gives the following result. 

I had a rock-salt prism constructed, so that the incidence 
on the first surface might be nearly vertical at the critical 
angle of total reflection, so as to avoid as much as possible 
any error arising from imperfections of the surface, or want 
of absolute equality of the angles at A and B; and likewise, 
that within the limits of the experiment, the loss of heat by 
reflection at the two surfaces might be nearly unaltered, as it 
is believed to be almost constant at incidences tolerably nearly 
perpendicular*. This prism, constructed for me by Mr. John 
Adie, had two angles of 40° and one of 100°; and so accu- 
rately was it made, that (satisfying myself with a careful mea- 
surement by the common goniometer, extreme nicety being 
unimportant) the angles appeared to be true to those quantities 
within a iew minutes of a degree. 

By a reference to Plate IV., fig. 1, it will now be under- 
stood that the required arrangement is of this kind. The 
heat diverging from the source S, is converted into an ap- 

* See Melloni on the Reflection oiWedAyAnmles de Oiimie, Dec. 1835. 



1 84 Prof. Forbes's Researches on Heat. \ 

proximately parallel beam by the lens L. It then passes 
through a diaphragm T, placed on one or other side of the 
prism (it does not much matter which, as the beam which 
arrives at the pile is always much wider than the second dia- 
phragm t, placed there to admit only the central rays arriving 
parallel to the line a c). The use of this diaphragm is, that 
a narrow enough pencil of rays may be employed, to be in- 
dependent of the variable breadth under which the surface 
of the prism is presented to the incident beam. The usual 
dimension of this diaphragm was one inch in breadth and one 
and a quarter in height, but in some instances its breadth was 
reduced to three-eighths of an inch. 

The pile p has its funnel-shaped orifice closed by a screen 
widi a vertical slit, an inch wide, in the direction of its axis. 
But there is a peculiarity in the arrangement of the pile very 
essential to the success of these experiments, where the pile 
itself is moveable, which I must not omit to mention. Its 
exposure to currents of air would render the observations, 
when the pile cannot be entirely inclosed by a box or screen, 
very capricious in its action. I therefore adapted to the end, 
bearing the conical reflector, an adjustable wooden tube r, 
containing a rock-salt lens, which still further increased its 
sensibility, and totally protected it from aerial currents. 

The abruptness of the effect of transition from partial to 
total reflection is far from being so complete as might be 
wished ; and this is easier accounted for than remedied. It 
arises mainly from the magnitude of the source of heat, the 
consequent want of parallelism of the refracted rays, the scat- 
tering of these rays in consequence of the imperfect polish of 
the surfaces, the unequal intensity of the rays in different 
parts of the section of the cylinder, and lastly, owing to the 
want of homogeneity of the rays of heat from any source, 
which the method would serve to measure, were the other 
imperfections removed, just as in the course of the total re- 
flection of light, prismatic colours are successively presented. 

My first rude attempts showed all this very clearly. As the 
diagonal ab of the lozenge (fig. 1) shortened, total reflection 
obviously succeeded to partial, and the change was not only 
very great, but near one point very rapid. The point where 
the most rapid increase took place, is obviously that where 
the greater proportion of the incident rays underwent total 
reflection, and might therefore be taken as a mean represent- 
ation of the quality of the heat. Still the change w^as too 
gradual to enable one by mere inspection to determine this 
point with accuracy, and I speedily resolved to take the sure 
but laborious method of ascertaining at a number of points 



Third Series. — Refrangihility of Heat. 185 

intermediate between total and partial reflection the intensities 
ol' the reflected heat, and by constructing a curve having 
measures of the diagonal of the lozenge (a function of the 
angle of incidence) for abscissae, and intensities for ordinates, 
I endeavoured to discover graphically for what vahie of the 
former the measure of the latter increased most rapidly, in 
other words, where the tangent made the greatest angle with 
the axis, or where was the point of contrary flexure of the 
curve. 

Plate IV. fig. 2, may represent such a curve. I have 
found that when the diagonal of the lozenge was 14*5 inches, 
the reflection was in all cases nearly total, or the galvanome- 
ter was little affected by any increase of the angle of incidence. 
This effect, measured by the vertical line A B, was denoted 
by 100. When the diagonal was increased to 15*0, the effect 
was reduced, we shall suppose, to 90, expounded by the line 
C D, at 15'5 by E F, and so forth. An interpolating curve 
drawn through the points so fixed, would have its greatest 
inclination to the axis A X, when, for a given variation of 
the diagonal, the decrement of the intensity was a maximum, 
in other words, at the determining angle for the predominating 
part of the heat used. Such a point of contrary flexure would 
therefore determine the mean index of refraction of the given 
kind of heat by the aid of the formula above investigated, 
whilst the form of the curve would lead to some conjecture at 
least, respecting the distribution of heat of the more or less 
refrangible kinds in the given ray. Heat of low refrangihility 
being the last to be totally reflected, would cause the curve to 
droop fastest near the extremity B, the more refrangible rays 
would be cut off' at the other end I of the curve. 

I lost no time in verifying the general truth of the principle, 
and also of the received doctrines respecting heat, by ex- 
amining the quality of the heat which reached the pile at dif- 
ferent stages of total reflection. If, as M. Melloni first ren- 
dered probable, heat of low temperature is least refrangible, 
and vice versa', and further, if it be admitted that such heat 
passes most difficultly through such substances as glass, it 
follows, that after total reflection has proceeded a certain 
way, so that the more refrangible, and therefore more trans- 
missible, rays have suffered total reflection, whilst the remain- 
ing rays constituting the primitive beam continue to be re- 
fracted, the heat thus reflected will be more copiously trans- 
mitted by glass, than when it came direct from the source. 
This conjecture was precisely verified. 

Subsequent experiment still more fully confirmed this result, 
and by showing that during the whole progress from partial 



186 



Prof. Forbes's Researches on Heat. 



to total reflection, the specific quality of the heat changes, gave 
countenance to the view that the gradation is in a great mea- 
sure owing to the want of homogeneity of the heat, and that 
the figure of the curve becomes (as we have said) a real test 
of the composition of a ray. 

At the inferior limit of the curve, or when partial reflection 
takes place, all kinds of heat are equally reflected (in the case 
of light, the light is white), just as at the superior limit, or 
after total reflection is complete, the beam has exactly the 
same relative composition as before. In the intermediate 
stages the composition is perpetually varying. The first rays 
totally reflected (and combining with the scattered and partially 
reflected rays) are the more refrangible, or those more easily 
transmitted by glass. At a certain point a maximum propor- 
tion of these enter into the reflected beam. As the angle of 
incidence becomes greater, more and more of the less re- 
frangible rays enter into the composition of the reflected heat, 
which at last possesses the same qualities as at first. This is 
well illustrated by the following early experiment which I made 
on the proportion of the reflected rays transmitted by a plate 
of glass '06 inch thick, at different stages of reflection (7th 
February 1838). 



Diagonal 
a b. Fig. 1 
in Inches. 


Deviations of Galvanometer. 


Ratio. 


REMARKS. 


Glass. j No Glass. 


14-5 

150 

15-25 

15-5 

15-75 

16-0 

16-5 


8% 13-75 
7-85 12-65 
7-1 1 10-9 
5-5 7-85 
3-4 51 
2-3 3-75 
1-45 2-3 


60:100 
62:100 
65:100 
70:100 
67 : 100 
61:100 

63:100 


Total reflection complete. 
Partial reflection. 



In the following experiments on the law of the transition 
from partial to total reflection, the arrangement was that 
shown in Plate IV. fig. J, and described (with the adjust- 
ments) in pages 182 — 1 84-; the centre of the pile p was 1 3 inches 
from the prism P, and the distance of the source of heat S 
from P was 12 inches; that a diaphragm T, whose aperture 
was 1 inch by 1|, was placed in the path of the ray usually 
between P and L near P ; the aperture of the pile was con- 
tracted to a breadth of one inch, whose centre was exactly in 
the line ad; and only that part of the prism was employed 
which was free from flaws capable of producing total reflection. 

The diagonal of the lozenge frame was varied from 14*5 
inches up to 16*5 or 17*0, about eight observations of the in- 



Third Series.'— Refrangibiliti/ of Heat. 



187 



tensity of reflected light being made at intervals. The series 
was then frequently reversed, and the mean results of the 
going and returning series taken to allow for any change 
which might have occurred in the intensity of the source. In 
all cases an observation of verification was made and such 
change allowed for. The dynamical effect on the galvano- 
meter was observed and noted. 

In reducing the observations the following plan was 
adopted. The intensity corresponding to the diagonal 14*5 
inches being assumed = 100, the other intensities were re- 
duced relatively to it, and projected, as explained in art. 60. 
By this means different series of observations became at once 
comparable with each other, and the beauty and regularity 
of the curves thus formed, and the almost perfect identity of 
those obtained on different days, and with different adjust- 
ments, give a degree of confidence in the results which is ex- 
tremely satisfactory. When from the nature of the heat the 
effect was very small (as in the case of alum being interposed, 
or the source being of low temperature), I have endeavoured 
to supply the deficiency by multiplying observations, and the 
uniformity of the curves thus obtained has been the test of 
my success. Where this test has failed (as in the attempt to 
work with heat of 212°), I have suppressed the results. 

Example. — Dark Hot Brass. March 31, 1838. 



Measure of 

Diagonal a 6, 

Plate xiii. Fig. 1. 

in Inches, 


Galvanometer.Needle. 


Excess. 


Ratio to Result 

with Diagonal 

= 14-5. 


stands at 


Swings to 


14-5 
150 
15-25 
15-5 

15-75 
160 
16-25 
16-5 


o 

A 0-1 
00 
0-15 
015 
0-3 
0-25 
015 
0-2 
0-15 


A11°0 
9-3 
8-0 
6-2 
6-3 
4-6 
3-15 
2-25 
1-9 


10-9 
9-3 
7-85 
6-05-1 
6-0 / 
4-35 
30 
2-05 
1-75 


100; 100 
85: 100 
72 : 100 

55 : 100 

40 : 100 
28 : 100 
19 : 100 
16 : 100 


14-5 


005 10-8 


10-75 



After the observations made as now described have been 
projected in the form shown, Plate IV. fig. 2, the diagonal 
corresponding to the maximum rate of decrease of the in- 
tensity was determined, for the purpose of deducing the index 
of refraction. The following enumerations of the kinds of 
heat employed, and the results derived from the several pro- 



188 



Prof. Forbes's Researches on Heat. 



jections, will give a just idea of the confidence due to the re- 
sults. 

Sources of Heat. — (1.) The direct rays of the Locatelli 
lamp. A slightly concave reflector was employed. (2.) The 
same lamp, with a reflector having the form of a portion of a 
sphere concentric with the wick ; the heat transmitted through 
alum. (3.) Heat from the same source transmitted by isoin- 
doiso glass '06 inch thick. (4-.) Heat from the same trans- 
mitted by opake black glass (through which the disk of the 
unclouded sun is just visible). (5.) Heat from the same trans- 
mitted through dark coloured mica, by which direct sunlight 
is absolutely stopped. This singular substance I long sought 
for in vain, it is unknown to many practical mineralogists ; it 
transmits green light at small thicknesses, when thicker its 
colour is hair-brovii'n. By reflected light its colour is between 
green and black. (6.) Heat from incandescent platinum. 
(7.) The same sifted by rvindoKso-glass as above. (8.) The same 
sifted by opake mica. (9.) Heat from dark brass about 700°. 
This is obtained from a nearly cylindrical cover of smoked 
brass placed over the flame of a spirit-lamp, so as entirely to 
conceal it, and which gives remarkably good results, without 
increasing considerably the angular breadth of the source 
(which is greatly to be avoided when a lens is used). It is in 
fact not much greater in size than the helical coil of platinum 
wire used in (6). (10.) The same, sifted by clear mica '0044 
inch thick. (11.) Heat from a crucible of mercury about 
450°. The crucible was about 2 inches in the side, smoked 
externally, and healed by a spirit-lamp. The temperature of 
the mercury which it contained (covered with sand) was noted 
at each observation by means of an inserted thermometer. 

The results were the following : 



Source of Heat. 



a h, or diagonal 

corresponding to the 

point of contrary flexure. 



/*, or Index of Refraction 
for mean rays computed 
by the Formula, page 183. 



Locatelli, direct 

-. with alum ... 

window-glass 

" opake glass 

. — — mica 

Incandescent platinum 

Ditto with glass 

opake mica 

Brass at 700° ..... 

Ditto with clear mica 
Mercury at 450° 

Mean luminous rays... 



15-49 
15-76 
15-65 
15-71 
15-6] 
1550 
15-66 
15-62 
15-45 
15-55 
15-50 

15-8 



1-571 
1-598 
1-587 
1-593 
1-583 
1-572 
1-588 
1-584 
1-568 
1-577 
1-572 

1-602 



Third Series. — Befrangihility of Heat. 1 89 

The preceding results give values of ju, all too high ; that for 
light is known by other methods to be only 1*53 or rs*. 
This arises from the increasing intensity of the partially re- 
flected light with the obliquity of the incident ray which makes 
the apparent transition from partial to total reflection too ra- 
pid, and consequently gives the index too great. The true 
indices may be approximately found by diminishing these 
numbers by '07 ; but the relative results are the most im- 
portant. 

The results which we have obtained apply, it must be re-^ 
collected, only to the 'predominant kind of heat in any source, 
and that we have as yet got no information respecting the 
composition of a ray and the amount of dispersion. 

It is very easy to see that were the mathematical conditions 
of the experiment (p. 183) fulfilled, we should be led to an 
exact analysis of heat, more perfect far than we have any 
prospect of obtaining in the case of light, considering the dif- 
ficulty of applying the photometer to coloured light. Were 
the curve in Plate IV. fig. 2, solely representative of the 
progress of reflection due to the heterogeneity of the rays, the 
increment of intensity between any diagonal E and another 
C, or DjT would denote the proportion of the entire heat in- 
cident, which lies between the limits of refrangibility assigned 
by the diagonal. Thus an entire ray would be decomposed 
into parcels of known proportions, between given intervals of 
refrangibility. The case is considerably different. Though 
the points of contrary flexure agree remarkably well, as we 
have seen, the curves are in some cases much more flattened 
than in others, where the source of heat is the same ; owing 
probably to the greater parallelism of the rays at one time 
than at another, depending on the distance of the source of 
heat from the lens. 

We can, therefore, in this way form but an imperfect idea 
of the comparative homogeneity of the different kinds of heat. 
Such comparisons can only be made advantageously by com- 
paring the results obtained in immediate succession from one 
and the same source with interposed screens of different qua- 
lities, as in the comparison which we instituted between heat 
direct from Locatelli's lamp, and that transmitted by glass, 
(p. 186). 

The facts respecting refrangibility, which may now be con- 
sidered as ascertained, serve to render our ideas much more 
precise in several respects. For instance, (1.) the range 
of mean refractive indices for heat is small, all the modifica- 
tions which we have considered lying within a range of "O^, 
or between \'5\ and 1*55 nearly, which is little more than 



190 Prof. Forbes's Researches on Heat. 

the commonly assigned dispersion of light, which for rock-salt, 
is between the limits r54- and 1*57 nearly. This, however, 
is for extreme rays of light, which can hardly be said of heat ; 
the extremes of dispersion are certainly much wider apart. 
(2.) The meafi refractive index of direct rays from different 
sources varies surprisingly little. In fact the differences for 
direct rays of heat from the Locatelli-lamp, incandescent 
platinum, and from a crucible heated to 450°, seem almost 
insensible, or within the limits of error of experiment. It is 
to be recollected, however, that this is compatible with the 
utmost variety in the composition of each. (3.) The effect of 
interposed screens in modifying the transmitted heat is very 
remarkable. These, so far as I have tried them, invariably 
raise the index of refraction, (alum, glass, opake glass, and 
opake mica for the Locatelli-lamp ; glass and opake mica for 
incandescent platinum, and clear mica for dark heat). This 
is the case even with those substances which suppress light 
altogether, and which therefore cannot be considered to do 
more than detach the heat of considerable refrangibility from 
the light which usually accompanies it, not as stopping the 
most refrangible rays and admitting the passage of those of 
lower temperature. Probably no substance acts in this way, 
though some (as black glass and mica, as the experiments of 
Melloni indicate) may probably absorb the heat spectrum at 
both extremities. It is probably to this source that we must 
attribute the very small fraction of heat transmitted by the 
black glass I used, being only that constituting the rays of 
the higher degrees of refrangibility, all those of Tow and mean, 
and also of the highest, degrees of refrangibility being pro- 
bably absorbed. (4.) With respect to the homogeneity of 
different kinds of heat, we can deduce nothing certain from 
the forms of the curves. They confirm, however, a view 
which I have long entertained, that heat from non-luminous 
sources is more homogeneous than any other. I argued this 
partly on the ground stated in p. 1 1 1 of this volume, and still 
more from the uniformity of results which I have in all classes 
of experiments obtained from dark heat, which often more 
than made up for the narrower range of the thermal effect, and 
which showed that the discrepancies observed in other cases 
were due not so much to errors of observation, as to unavoid- 
able changes in the character of the heat, (p. 100). This re- 
sult is the more probable from the size of the source of heat 
necessarily used in the crucible experiments (p. 188), which 
tends to render the passage from partial to total reflection 
more gradual, and thus to flatten the curve. To the same 
cause may also probably be attributed the somewhat greater 



Third Series. — Refrangihility of Heat. 191 

index of mean refraction obtained for heat from this source 
than that of dark heat of higher temperature. 

The following method might perhaps be used with success 
for obtaining more exact data respecting the refrangihility, 
and especially the dispersion, of heat, than that just described 
pretends to give. It must insure a beam of parallel rays of 
heat of sufficient intensity and uniform in every part of its 
section. A small point of heat placed behind a lens (or two 
or three lenses to diminish aberration) is the most obvious 
plan. But the intensity would be inadequate. I would, 
therefore, propose a platinum wire, heated by one of Mr. 
Daniell's constant voltaic batteries, placed behind a refracting 
semicylinder of rock-salt*. The central rays should be alone 
employed, and the prism for total reflection should be high 
and narrow as well as the aperture of the pile. It is possible 
that in this case the transition from partial to total reflection 
would be so rapid as to make the error arising from the 
varying intensity of partial reflection inconsiderable. By 
changing the force of the battery, heat of all temperatures 
might be employed in succession. The numerical analysis of 
the heat spectrum would then take place as described in 
p. 189. 

Conclusion. — My object in these, as in former researches, 
has not been to group experiments of mere curiosity indiscri- 
minately selected, but to present a basis for a proper theory 
of heat. Without some such end in view I should have 
thought the time and labour spent on these experiments in 
some degree misapplied. Mere numerical results, though 
ultimately of the highest consequence to science, should never 
form the exclusive object of the philosopher. I trust to have 
shown that though many of the conclusions in this paper are 
based upon quantitative results, these have not been the ulti- 
mate aim of the inquiry. 

The mutual bearing of the three sections of this paper, and 
of all upon what (from analogy to physical optics) we may call 
physical thermoiics, is now evident. (] .) In the first section we 
have minutely discussed a point apparently perhaps of minor 
importance, namely, the unequally polarizable nature of the 
rays of heat. The importance of the doctrine lies in this : 
that the common theory of undulation recognises no such 
variation, nor perhaps does it exist in the case of light (I 
know, however, of no decisive experiments on this point), with 
the exception of the small effect due to the difference of re- 
frangihility. Now, having proved in the third section that 
this difference of mean refrangihility is from most sources 

* Such a one I have had executed. 



192 Prof. Forbes's Researches ofi Heat. 

very small, which yet differ widely in their polarizability, we 
infer that that explanation is probably inadequate, and that 
w^e must look for a mechanical theory of heat differing in 
some particulars from that of light. 

(2.) This latter conclusion is further confirmed by the re- 
sults of the second section, in which is deduced, from the 
singularly accordant results of wholly distinct series of experi- 
ments with heat from those distinct sources, that the phae- 
nomena of depolarization differ surprisingly, numerically/ 
speaking, from those of light, whilst in their general character 
they are entirely similar. The results at which we have ar- 
rived oblige us to admit, either that the length of a wave of 
heat is several times greater than that of a wave of light, or 
that the velocities of the ordinary and extraordinary ray in 
doubly refracting crystals are totally different from those of 
light ; or else a combination of these hypotheses. Now, of the 
two first alternatives, we are bound at present, I think, to 
prefer the latter, since we know nothing of the pheenomena of 
double refraction but from this experiment ; whilst the sub- 
sequent experiments on the refractive index, would, according 
to the prevalent theory of dispersion, seem to show that the 
mean length of a wave of heat cannot differ very materially 
from one of light. This amounts to admitting that the doubly 
refractive energy is more feeble for heat than for light; in 
other words, that a greater thickness of a crystal is required 
to produce a given effect. The second and third sections 
also confirm one another in this respect, that the uniformity 
of the results of depolarization with heat from different sources, 
and also of the refrangibility, would both be highly impro- 
bable did the length of a wave materially differ in those in- 
stances. 

(3.) Of the results of the third section, I have already 
spoken at sufficient length (p. 189). The mean index of re- 
fraction for all kinds of heat tried is less than for light; — it 
ranges within narrow limits; — when the heat from different 
sources is unmodified by transmission through diathermant 
bodies, these limits are very narrow indeed; — the measure 
of dispersion is considerable but unascertained, and opens a 
fair field for experiment; — dispersion is probably least for 
sources of low temperature. 

Such are the chief data for speculation afforded by the ex- 
perimental results contained in this paper: — too imperfect 
perhaps in themselves to form the basis of a mechanical theory 
of heat, yet such I hope as may be considered to be fit con- 
tributions towards its construction at a future period. 

Edinburgh, April 16, 1838. 



C 193 3 

XXV. Researches on Suppuration. By George Gulliver, 
Esq., Assistant Surgeo7i to the Royal Regiment of Horse 
Guards. 

Sect. I. — On the frequent presence and on the effects of Pus 
in the Blood, in diseases attended by Inflammation and Suppu- 
ration.* 

f N the prosecution of an inquiry in which I have been long 
* engaged concerning Inflammation and Suppuration, I soon 
perceived the necessity of instituting a careful examination of 
the blood in these affections, and particularly in the different 
forms of inflammatory fever and hectic. 

The result has been the detection of pus in the blood in 
almost every instance in which there was either extensive sup- 
puration, or great inflammatory swelling without a visible de- 
position of pus in any of the textures of the body : and the 
contamination of the blood by pus appears to me to be the 
proximate cause of the sympathetic inflammatory, sympathetic 
typhoid, and hectic fevers. Since the writings of Dr. Lee, Mr. 
Lawrence, Mr. Arnott, of MM. Velpeau, Dance, and others, 
the profession has become familiar with cases in which pus has 
been found in the veins, particularly after surgical operations 
and in uterine phlebitis ; but although the humoral patho- 
logy has of late years begun to assume some of its ancient im- 
portance, I am not aware that any writer has attempted to 
demonstrate the dependence of the fevers under consideration 
on the presence of pus in the blood. 

Previous to a brief notice of some of the experiments and 
observations from which the results have been drawn, it may 
be proper to mention the means by which I have detected pus 
in the blood. The examination was very simple, — partly 
chemical, and partly by the aid of the microscope. Those 
who are acquainted with the minute constitution of the animal 
fluids are aware of the rapid and energetic action of water on 
the blood-corpuscles : now the globules of pus undergo no 
change after having been long kept in water ; accordingly, 
if the suspected blood be mixed with this fluid, the blood cor- 
puscles will soon become invisible, and any globules of pus 
that may be present will subside to the bottom of the vessel, 
and may be easily seen, and their characters determined, with 
a good microscope. Ammonia instantly renders the blood- 
corpuscle invisible, while that of pus is acted on but slowly 
by the alkali; and the different action of acetic acid on pus 

• Read before the Royal Society, June 14, 1838 ; and now communicated 
by the Author. 

Phil. Mag. S. 3. Vol. 13. No. 8L SepL 1838. O 



194 Mr. G. Gulliver's Researches oti Suppuration. Sect. I. 

and blood is equally remarkable. Hence I have employed 
these agents advantageously in conjunction with the other 
means; and I have also seen pus-globules in the blood, though 
rarely, without any preparation. With water, however, the 
examination is most easy, simple, and satisfactory, if the ob- 
server be thoroughly familiar with the microscopic characters 
of the fluids under examination. A good instrument, never- 
theless, is necessary; and the admirable deep object glass of 
Mr. Ross is the one I have principally employed. It is hard- 
ly necessary to add, that chyle-globules are not likely to be 
mistaken for those of pus, since, independently of other di- 
stinctions, the medium diameter of the latter is at least TtrW^^^ 
of an inch, which is above twice that of the former. 

Exp. 1. A weak solution of corrosive sublimate was in- 
jected into the subcutaneous cellular tissue of a dog's thigh ; 
great swelling of the limb took place, and he died forty-five 
hours after the injury. A good deal of serum mixed with 
fibrine was found in the cellular tissue of the thigh, but there 
was no purulent deposit. 

Several pus-globules were detected in some blood obtained 
from the right ventricle of this dog's heart. 

Exp. 2. A large dog had both his tibiae injured by some 
operations connected with necrosis ; great swelling of the 
limbs, with violent fever, succeeded, and he died forty-three 
hours subsequently. 

A large quantity of fibrine was found effused into the cel- 
lular tissue of the extremities, mixed, in one of them, with a 
very scanty proportion of purulent matter. 

In some blood, obtained from the vena cava, numerous glo- 
bules of pus were observed. 

Exp. 3. An irritating fluid was injected into the perito- 
neum of a dog ; he had great thirst, refused food, and died 
the third day after the operation. 

A large quantity of coagulated lymph and sanguinolent se- 
rum with some pus was found in the belly. 

In some blood obtained from the inferior cava vein many 
globules of pus were seen. 

Exp. 4. Two ounces of pus were injected into the left 
pleura of a dog, and very carefully confined there ; he was 
thirsty and feverish for fifty-five hours after the operation, 
when he was killed. 

An ounce of fluid, almost entirely serum, was found in the 
pleura, and some fibrinous exudation on the membrane. 



Mr. G. Gulliver's Researches on Suppuratio7i. Sect. I. 195 

Blood from the heart, as well as from the vena cava was 
examined, and found to contain several pus globules. 

Exp. 5. Four ounces and five drams of pus were injected 
into the peritoneum of a dog, and the wound carefully closed ; 
he died thirty-seven hours after the injury. 

There were only nine drams of a sero-sanguinolent fluid 
found in the peritoneum, and a considerable quantity of co- 
agulated lymph on the membrane. 

Pus was detected in the blood. 

Exp. 6. Half a dram of pus, mixed with half an ounce of 
water, was gradually injected into the crural vein of a dog. 

Some fever followed, and he refused solid food for two days, 
but recovered at the end of a week. 

The same quantity of pus was soon afterwards injected into 
the other crural vein, when similar symptoms were produced, 
and he perfectly recovered in a few days. 

Exp. 7. Six drams of pus having been injected into the 
crural vein of another dog, he was not much affected at first, 
but in a few hours became very weak, was stupid, thirsty, 
and refused his food. After thirty hours he took but little 
notice of surrounding objects, his respiration was hurried, and 
he died thirty-six hours after the operation. In the blood of 
the inferior cava some pus globules were readily detected. 

Case 1. A girl died of confluent small pox on the ninth 
day of the disease. There was great swelling of the integu- 
ments. 

In the blood of the right ventricle numerous pus-globules 
were found. 

Case 2. A woman had confluent small pox, uncomplicated 
with erysipelas or inflammation of the viscera. 

On the eighth day of the disease some blood was drawn 
from a vein in the arm : several pus-globules were found in 
this blood. 

Case 3. A male child, ast. 15 months, died on the ninth 
day of small-pox. Only a few pustules appeared, and these 
were imperfectly developed : there was considerable swelling 
in the face, slighter in other parts. 

At the post-mortem examination, it was observed that a 
small quantity of a white opake fluid might be squeezed from 
the cut surfaces of the lymphatic glands of the ne<3k and groin : 
this fluid had the microscopic and chemical chars* ,>*rs of pus. 

In some blood obtained from the right ventrucl^^i and from 
the inferior cava vein, pus was detected. 

02 



196 Mr. G. Gulliver's Researches on Suppuration. Sect. I. 

Case 4. In a woman who died of puerperal peritonitis, the 
peritoneum contained a large quantity of coagulated lymph, 
serum, and purulent matter. 

Pus was detected in the blood obtained from the right ven- 
tricle of the heart. 

Case 5. James Green, set. 27. was admitted into hospital 
with an ulcer of the leg. Seven days afterwards, the limb be- 
gan to swell, and there was hardness in the femoral vein, with 
some redness in the course of the absorbents on the inner side 
of the thigh. The swelling of the limb increased gradually ; 
he had first pain in the head, thirst, and quick pulse ; then 
purging, pain in one wrist, with restlessness, incoherency of 
speech, and offensive breath ; finally, low muttering delirium, 
accelerated respiration, and coma preceded his death, which 
took place on the twelfth day after his admission into hos- 
pital. 

At the post-mortem examination, the large veins of the 
limb were found to be occluded throughout by firm clots of 
blood, mixed with pus and coagulated lymph, and the lining 
membrane of the femoral vein was in many places of a red co- 
lour, and coated with fibrine. In the iliac vein no such signs 
of inflammation appeared, although there was a large coagulum 
of blood, which had lost its red colour, containing in its centre 
a small quantity of matter resembling pus. Several purulent 
deposits presented in the sheath of the femoral vessels, and in 
the intermuscular cellular substance. 

The matter resembling pus in the clot of the iliac vein had 
neither the chemical nor microscopical characters of that fluid. 

In some blood obtained for examination from the right ven- 
tricle and from the vena cava, numerous globules of pus were 
found. 

Case 6. James Hawke, set. 22, had a superficial wound of 
the tibia, followed quickly by considerable pain and swelling. 
There was a very scanty deposit of pus in the subcutaneous 
cellular tissue. The swelling of the limb increased and ex- 
tended rapidly, the integuments becoming discoloured, and the 
slight suppuration ceasing. His dissolution was preceded by 
subsultus, collapsed face, accelerated breathing, hiccough, and 
coma. 

The swelling of the limb was found to be produced by ef- 
fusion of fibrine and sanguinolent serum. A few pus-glo- 
bules were found in the blood obtained from the vena cava. 

Case 7. M. Jackson, ast. 42, had erysipelas of the face, 
which decreased, and was succeeded by jaundice and effusion 



Mr. G. Gulliver's Researches on Suppuration. Sect. I. 197 

into the pleura. He became listless and low, with accelerated 
respiration, and died six days after the appearance of the ery- 
sipelas. 

An ounce of turbid serum, with a little purulent matter, was 
found in the right pleura, and eight ounces of sanguinolent 
serum in the left. 

Some blood was obtained for examination from the larger 
veins, and found to be greatly contaminated with pus. 

Case 8. Sergeant Dunn, aet. 29, had profuse suppuration 
between the muscles and beneath the integuments of the thigh; 
he died, after some weeks' suffering, exhausted by hectic. 

The purulent matter was extremely offensive, putrefying 
with great rapidity, and sometimes coagulating spontaneously, 
when set aside for a short time. It was poor in true pus-glo- 
bules, but contained a large quantity of flaky fibrinous matter, 
to which its opacity was chiefly owing. Many pus-globules 
were found in the blood obtained from the right ventricle. 

Case 9. Wm. MacLean, aet. 1 9, died of pulmonary con- 
sumption. In his lungs were several vomicae, containing pus 
and softened tubercular matter. 

In the blood obtained from the vena cava and right ven- 
tricle, many pus-globules were found. 

Case 10. A man had irritative fever, in the Marylebone 
Infirmary, consequent on a large abscess behind the trochanter 
femoris. 

An ounce of blood was drawn by cupping from the neigh- 
bouring sound parts, and some pus was detected in this blood. 

Case 11. An officer's charger died with vomicae and tuber- 
cles in the lungs, and sero-purulent fluid in one pleura. Some 
time before his death his respiration and circulation were 
much accelerated. 

The vomicae contained pus mixed with gangrenous sanies. 

In the blood obtained from the vena cava inferior pus was 
detected. 

The preceding instances by no means comprehend the 
whole number in which I have found pus in the blood. In 
the detail I have rather been anxious to give examples of in- 
teresting varieties, than to increase the number by needless 
repetitions. 

It is satisfactory to add, that the observations of Dr. Davy 
tend to confirm the accuracy of those which I have just rela- 
ted. He detected pus in the blood of consumptive patients, 
after my general results had been subjmitted to him, but be- 



198 Mr. G. Gulliver's Researches on Suppuration. Sect. I. 

fore I had turned my attention to the state of the blood in 
phthisis. He has lately informed me that he has found pus 
in the blood in seventeen instances after death, in sixteen of 
which there was declared suppuration, and in one none could 
be detected : in the latter, the patient died of acute inflam- 
matory disease. 

Before considering the conclusions to be deduced from the 
preceding observations, it may be proper to advert briefly to 
the nature and use of suppuration, although I shall have oc- 
casion to bring forward the evidence on matters of opinion in 
a more systematic form in a future part of these researches. 

Since the microscopic observations of Mr. Hunter, Sir Eve- 
rard Home, and Mr. Bauer, the opinion has often been ex- 
pressed in this country, that the globules of pus are nothing but 
those of blood, modified by the inflammatory process. I be- 
lieve Sir Astley Cooper and the late Dr. Young came long ago 
to this conclusion. Finally, on the continent, M. Gendrin, 
without much regard to the observations of English patho- 
logists, adopts precisely the same theory, supported indeed 
by a series of very ingenious experiments, which have been 
generally considered conclusive on this subject. 

I have repeated the experiments of M. Gendrin with great 
care, and although I see no reason to dissent from that part 
of his conclusion already stated as having been long since ad- 
vanced in this country, I have not been able to observe the 
phaenomena related in his work. It seems not improbable 
that M. Gendrin was influenced by the erroneous views of 
M. Milne Edwards as to the globular structure of fibrine; for 
M. Gendrin states in one place that pus is but a modification 
of fibrine, although in others he informs us that it is a trans- 
formation of the blood-corpuscles that constitutes suppuration. 
By cauterizing the web of a frog's foot under the micro- 
scope, or by elevating on the polished blade of a lancet a film 
of the edge of a wound previously made in the part, he as- 
sures us how easy it is to see the blood-particles gradually 
transformed into those of pus. I regret to say that I have 
not been able to succeed in this observation, because I found, 
after repeated trials, that I could not by any means induce 
suppuration in batrachian reptiles. 

With regard to the conversion of clots of fibrine into pus, 
some experiments to be adduced in another section of this in- 
quiry, render it extremely probable that the matter often found 
in the centre of such clots in the heart and great vessels, is 
nothing more than softened fibrine ; and which, although it 
resembles pus in some particulars, presents neither the che- 
mical nor the microscopical character of that fluid. I have 



Mr. G. Gulliver's Researches on Suppuration. Sect. I. 199 

seen nothing like pus-globules in the softened fibrinous clots 
of the heart ; and the rounded particles which sometimes oc- 
cur in softened coagula of veins are probably the remains of 
blood-corpuscles. The conversion of the latter into those of 
pus is extremely probable, and it is equally probable that 
this change may take place either in the capillaries or out of 
them. In the former case, after the stagnation of the blood 
in these vessels which preceded the suppurative process, as 
the clot softened and the pus became mature, it would be car- 
ried into the circulation, and hence its presence in the blood 
independently of wounds or abscesses. 

In instances of idiopathic or traumatic phlebitis, the man- 
ner in which the pus may become mixed with the blood is ob- 
vious enough. There is a class of cases to which the latter 
appellation is commonly applied, which are probably not ex- 
amples of inflamed veins. They seem rather to be of an op- 
posite nature; for I have seen large veins, which had been di- 
vided many days before death, containing purulent fluid, al- 
though their inner surfaces presented no marks of inflamma- 
tion ; f nd the total failure of this process in them would seem 
to have left open their wounds, so as to favour the entrance 
of pus into them from the neighbouring parts : and this con- 
sideration would involve an important point of practice. 

It might be asked if, on a suppurating surface, the pus-glo- 
bules, considerably larger than those of blood, escape from 
the capillaries, how comes it that the latter pai'ticles do not 
escape as well ? To which it may be answered, that the dis- 
charge of the pus-globules is preceded by the coagulation of 
the blood in these vessels ; and that their closure, where there 
is a breach of continuity, is provided for by the formation of 
the clot keeping pace with its decomposition during the sup- 
purative process ; and the blood corpuscle, reduced in size 
by being broken down, or by losing its external part, may 
escape, and still become enlarged out of the vessels from the 
addition of new matter, till it assumes the character of a true 
pus-globule : hence its larger and more unequal size and 
irregular surface than the blood corpuscle. 

I think my experiments will render it probable that suppu- 
ration is a sort of proximate analysis of the blood. As the 
eifused fibrine produces swelling, or is attracted to the conti- 
guous tissue for the reparation of injury, the blood corpuscles, 
altei'ed by stagnation, become useless, and are discharged in 
the shape of pus, as waste from the system. Suppuration, 
therefore, would appear to be a physiological rather than a 
pathological phaenomenon — pus being an excrementitious dis- 
charge — a part of the blood which has become efi'ete and 



200 Mr. G. Gulliver's Researches on Suppuration. Sect. I. 

noxious during the repai-ative process, whether this process 
may have been employed in limiting the extent of an abscess 
or in healing breaches of continuity. If, however, there should 
be a formation of pus in the capillaries, in consequence of the 
stagnation and coagulation of their contents, this pus might 
be mixed in large quantities with the blood in cases where 
there was no declared suppuration, as in some of the examples 
brought forward in this paper. 

With regard to the correct observation of Miiller, that the 
smaller capillaries have only the diameter of a blood cor- 
puscle, I shall on a future occasion show, from the result of 
experiments, that these vessels become sufficiently enlarged 
during inflammation to contain a row of pus-globules. 

If it should be remarked that pus is often formed without 
any obvious addition of fibrine to the neighbouring parts, it 
should be recollected that this is not a healthy, but a diseased 
form of suppuration ; and the distinction and explanation 
are not difficult. In the formation of the unhealthy pus in 
question, the fibrine is broken down, mixed, and excreted 
with the pus ; and hence the flaky, curdy appearance of such 
matter, its proneness to putrefaction, and the cases cited by come 
authors as instances of suppuration without inflammation, 
and the old term, " badly matured matter." Independently 
of the paucity of true pus-globules in this kind of discharge, 
with the abundance of flaky particles, its tendency to putre- 
faction would affiard strong proof of its containing fibrine but 
little changed in its composition ; for of all the animal fluids, 
pus is probably that which resists putrefaction with the greatest 
pertinacity. The eighth case, that of Dunn, is but one among 
many that I could cite in illustration of these observations. 

It remains to deduce the conclusions from the experi- 
ments and observations related in this paper. 

The term suppurative fever is not new, and its signification 
is probably now extended ; for it seems to be an appropriate 
one for the different forms of constitutional disturbance under 
consideration. If the presence of pus in the blood and the 
fever in these cases be not related as cause and effect, the 
coincidence would appear to be no less interesting than re- 
markable. 

What a field of inquiry this view opens to us ! Henceforth, 
whenever a patient is affected with inflammatory fever, or 
that low typhoid state which is so generally a forerunner of 
death, as a consequence of traumatic or idiopathic inflam- 
mation, the state of the blood will present an interesting sub- 
ject of investigation. And this is not merely a matter of cu- 
riosity; for the question will arise, whether, in the treatment 



Mr. G. Gulliver's Researches on Suppuration. Sect. I. 201 

of such cases, it would not be advantageous to produce sup- 
puration as soon as possible on the surface of the body, so as 
to establish a drain by which the blood might be deprived of 
the offending matter. It may be asked also, whether the be- 
nefit so often effected by blisters, setons, and issues, in certain 
internal inflammations, — or by incisions, which cause sup- 
puration, in inflammatory affections of the integuments, be not 
explicable by this theory? It is well known that in cases of 
traumatic or idiopathic inflammation, attended with great 
swelling and febrile excitement, the establishment of suppu- 
ration in the part is generally a favourable symptom, the se- 
paration of the pus from the blood being a sort of crisis to the 
symptomatic fever. In small-pox, it is a popular belief that 
" the striking in," as it is termed, or suppression of the pus- 
tules, is a bad symptom; and this is so far true, that the 
worst cases of this disease are those in which there is great 
swelling of the integuments without the due formation of pus 
in the usual situation. In every instance in which I have ex- 
amined it, I found pus in the blood of patients aff'ected with 
small-pox. 

In the fourth and fifth experiments the pus which was in- 
jected into the serous sacs would appear to have been absorbed. 
A more careful inquiry, however, would be requisite to warrant 
this conclusion ; for in some experiments made by Dr. Davy, 
the quantity of matter injected seemed to be increased; and I 
have since made an experiment with the same result. 

The absorption of pus being the cause of hectic fever is an 
old hypothesis, which the detection of pus in the blood in 
cases of chronic abscess and in pulmonary consumption might 
be supposed to confirm. It does not seem necessary, how- 
ever, to assign two causes for one effect. When pus in large 
quantities is incessantly forming in the capillaries, it is easy 
to imagine how it may become mixed with the blood. 

I have related instances of pus in the blood, independently 
of suppuration out of the vessels : this fact appears to be of 
some importance, for it must be inferred that the pus was not 
absorbed, but formed in the blood. 

If it be objected to some of the foregoing views, that pus 
and extravasated blood are often absorbed without any ill 
effects, and that no constitutional disturbance may ensue after 
inflammation and the consequent effusion of fibrine — it may 
be remarked, first, that pus and blood are probably absorbed 
in a modified state ; and secondly, that a small quantity of 
pus, like other poisons, gradually added to the circulation 
may not be productive of bad symptoms. The sixth and 
seventh experiments may be cited in illustration. It is pro- 



202 Mr. J. J. Griffin's Instructions for the 

bable that the degree and type of the fever induced by the 
presence of pus in the blood may be found to depend on the 
extent to which it may be contaminated. 

Of the inflammatory, hectic, and low typhoid fever, it seems 
hardly necessary to observe, that they appear to be all com- 
prehended under the common designation of constitutional 
irritation in the interesting work of Mr. Travers, which I had 
not read till my attention was directed to it by Mr. Liston 
after this paper was written. Under the term typhoid, I have 
included that grave form of fever in which the vital powers 
sink rapidly, as I believe, from somewhat sudden and exten- 
sive mixture of pus with the blood, as sometimes occurs after 
operations on veins, or amputations, or even independently 
of wounds. The patient seldom complains of much pain ; he 
has, among other symptoms, dilated nostril, flushed face, en- 
crusted tongue and teeth, restlessness, small quick pulse, 
cold clammy sweats, offensive breath, hiccough, subsultus, 
stupor. 

I cannot conclude this paper without expressing a hope 
that it will lead to a still more careful and extensive examina- 
tion of the blood in various diseases than has hitherto been 
attempted. The microscope may become as important an 
instrument to the pathologist, and even to the medical practi- 
tioner, as the stethoscope. If my results should be confirmed, 
it is hardly too much to expect that some important discovery, 
particularly in diagnosis, may be made by a patient investi- 
gation of the blood in many malignant diseases, such as 
cancer : it is not long since the urinous fever, as it is called, 
was found to depend on the accumulation of urea in the 
blood. 

XXVI. Instructions for^the Qualitative Analysis of Soluble 
Salts. By John Joseph Griffin, Author of " Chemical 
Recreations."* 

[The salts are supposed to be in a state of purity, and each to contain one 
of the twenty-seven metals, and one of the fourteen acids, that are 
named in the tables.] 

ir^ISSOLVE the salt in water, and apply to separate small 
-■-^ portions of the resulting solution contained in test tubes, 
or in conical test glasses, a few drops of the test solutions that 
are named at the head of each column in the tables, com- 
mencing with those on the left hand. 

Pay no attention to the precipitates that are not mentioned 
in the tables. 

* Communicated by the Author. 



Qualitative Anali/ns of Soluble Salts. 



205 



PRECIPITANTS FOR METALS LN SALTS. 


Solutions to be Neutral. 


Solutions 

to be 
Acid. 


METALS 

indicated by the 

Precipitates. 


ll 


i 

s 
o 

a 

B 

< 


Potesh. 


Red Prussiate of 
Potash. 


None 
None 
None 










1 Potassium. 

2 Sodium. 

3 Ammonium. 




None 
None 
None 








4 Barium. 

5 Strontium. 

6 Calcium. 






White 
White 
White 
White 
White 


All 5 are 
insoluble 
in excess 


Brown 

Blue 

None 


Yellow 
Black 


7 Manganese. 

8 Iron, protosalts 

9 Magnesium. 

10 Cadmium. 

11 Bismuth. 






White 
White 
White 
White 
White 
White 


All 6 are 
soluble 
in excess 


Yeilow-Red 
White 


None 
Black 
Yellow 
Orange 


12 Zinc. 

13 Tin, protosalts, 

14 Aluminum. 

15 Lead. 

16 Tin, persalts. 

17 Antimony. 






Black, 
seeGoldNo.25. 


Red-Brown 




18 Mercury, its 

protosalts. 

19 Cobalt. 

20 Copper. 






Blue, 

If boiled. Red. 
Bine, 
If boiled. Black. 










Green 
Green 
Green 


Yellow-Green 

None 
Light-Blue 




21 Nickel. 

22 Chromium. 

23 Iron, persalts 
and protosalts 
mixed. 






Yellow, 

Yellow, 

sometimes slight 
and Black. 


Yellow-Red, 
But none from 
the Perchloride. 
None 




24 Mercury, its 

persalts. 

25 Gold. 






Brown 
Brown 


None 
Brown 




26 Iron, persalts. 

27 Silver. 



204- Instructions for the Qiialitative Analysis of Soluble Salts. 

SUPPLEMENTARY TESTS. 

For Nos. 1, 2, 3, of the metals. 

Salts of Ammonia give the odour of ammonia when 

warmed with a few drops of a solution of potash. 
Salts of Soda held in a dry state in a small blue flame 

colour it yellow. 
Salts of Potash do neither. 
For Nos. 4, 5, 6, of the metals. 

Salts of Barytes give precipitates with solutions both of 

the yellow and the red chromate of potash. 
Salts o( Strontian with the yellow chromate alone. 
Salts of Lime with neither. 



PRECIPITANTS FOR ACIDS IN SALTS. 


Nitrate of Barytes. 


Nitrate 

of 
Silver. 


Nitrate 

of 

Lead. 


Ciiloride 

of 
Calcium. 


SALTS 

indicated by the 

Precipitates. 


None 
None 
None 
None 
None 
None 


None 
None 
White 

Black 


Yellow 
White 




1 Nitrates. 

2 Chlorates. 

3 Chlorides. 

4 Iodides. 

5 Arsenites. 

6 Sulphurets. 


White 
White 
White 
White 

White 


All 5 soluble in 

Nitric Acid, 
without Efferves- 
cence. 


None 

Yellow 

Brown 




White 

Sol. in water 

White 

Insol.inwater 


7 Fluorides. 

8 Phosphates. 
.9 Arseniates. 

10 Borates. 

11 Oxalates. 


White 


Soluble in Acids 
with Effervescence 








12 Carbonates. 


White 


Insolublein Acids 








13 Sulphates. 


Yellow 










14 Chromates. 



SUPPLEMENTARY TESTS. 

For Nos. 1, 2, of the acids. 
Dry Nitrates heated with dry bisulphate of potash in a 

glass tube, produce a red gas. 
Dry Chlorates do not. 

Easy method of applying Sulphuretted Hydrogen Gas as a 
Test. — Take a test tube, an inch wide and six inches long. 
Put into it half a grain of sulphuret of iron, or sulphuret of 
antimony, and two or three drops of muriatic acid. Insert 
into the mouth of the tube a slip of white paper, three inches 



G. Th. Fechner's Justification of the Contact Theory. 205 

long and half an inch wide, wetted with the solution under 
examination previously acidified. Allow a portion of the paper 
to project beyond the tube and secure it by inserting a cork. 
Warm the bottom of the tube over a spirit-lamp. The action 
of the gas on the solution is manifested by the change pro- 
duced in the colour of the paper. As in Nos. 10 and 11, 
Table I. you have only to distinguish between black and yel- 
low, and in Nos. 14 — 17, between no change, black, yellow, 
and orange, all of which are easily perceived upon white 
paper, this method of testing accomplishes the object equally 
as well as the more operose and disagreeable methods in com- 
mon use. 

Glasgow, May 1, 1838. 



XXVII. Justification of the Contact Theory of Galvanism. 
By G. Th. Fechner.* 

T^HE present memoir was already complete before I re- 
ceived Pfaff's late work ^* Revision der Lehre vom Gal- 
vano-Voltaismus" which has in general the same object in 
view. As I find that Pfaff's experiments refer rather to other 
points of the subject than to my own, I think that this paper 
will not have been rendered superfluous by that work, but 
that the one may serve as the completion of the other. 

The chief arguments which can with any appearance of 
weight be brought to bear against the theory of contact, and 
in favour of the chemical theory, have lately been brought 
together by the zealous supporter of the latter, De la Rive, in 
a separate work " Recherches sur la Cause de VElectr. Volt. 
1 836." I shall chiefly refer to this, especially since the parti- 
sans of the chemical theory rest principally on De la Rive's 
experiments. Faraday's late experiments militate not so 
much against the voltaic theory as (at least apparently so) 
against a theory which seeks for the origin of electricity 
solely in the contact of metals with each other, on which sub- 
ject I shall at the conclusion have occasion to add a few 
words. Moreover they have been, together with the experi- 
ments of Karsten, which may be considered in the samfe light, 
treated of in detail by Pfaff; I can therefore pass them over 
at present. I have myself my own opinion on the subject, 
which I would rather produce at another time and with experi- 
ments, than at present with words. As to the following ex- 
periments, I have frequently repeated and varied them, in order 
to derive the expression from facts, not from accidents, from 

* From Poggendorff's Annalen, vol. xlii. p. 48). Translated by Mr. 
W. Francis. 



206 G. Th. Fechner's Justification of the 

which, I confess, I do not consider De la Rive's experiments 
to be entirely free. 

I. Facts iichich refer to the unclosed circuit. 

1. I have given in these Annals (vol. xli. p. 225) the means 
of proving with certainty the not inconsiderable amount of 
electricity which two heterogeneous metals acquire by contact 
in an insulated state. The supporters of the chemical theory 
are accustomed either to deny the certainty of these experi- 
ments, a denial which will henceforth be rendered impossible 
by the application of the methods here stated, or to derive 
the electricity thus originated from friction, pressure, or the 
chemical influence of the air and its moisture. It is to be 
shown that the result cannot depend on these. I must how- 
ever remark previously, that it appears to me somewhat 
strange to allow to friction and pressure, which after all are 
only particular modifications of contact, the property of ex- 
citing electricity, independent of chemical action, while it is 
so obstinately denied to the simple contact. Nor has it even 
once been tried to derive thermo-electricity from chemical 
action: the agency of contact is here undoubted. 

That the result, in the above-mentioned experiments, can- 
not depend on friction, has already been shown in my memoir 
in these Annals, vol. xli. p. 235, under No. 4.*. That it does 
not depend on pressure, is evident partly for this reason; that 
wherever the contact is completely effected, which naturally 
cannot take place entirely without pressure, an increase of the 
pressure does not indicate any more evident influence on the 
power of the shocks ; and partly, that, according to the experi- 
ence of Becquerel (so very extensive on this subject) all bodies 
are capable of having electricity excited in them by pressure, 
with the single exception however of the case, in which both 
bodies pressed together are good conductors, in which it at 
least cannot be demonstrated, undoubtedly for the same rea- 
son which hinders the demonstration of the electricity pro- 
duced through the friction of two good conductors. But 
that chemical action cannot be the cause of the result follows 
already indirectly for this reason ; that in this case the con- 
densation of the electricities at the surfaces of contact would 
be entirely inexplicable, which on the other hand is very easily 
explained according to the voltaic theory. In fact, it is self- 
evident, that, if a force exists in the contact of both plates, 
which can separate and transfer to the respective plates the 
electricities, notwithstanding their attraction for each other, it 
must also be capable of keeping them separate in a degree 
proportional to the intensity of that force. 

* The statement here alluded to will be given in the sequel of this 
translation. Edit. 



Contact Tlieory of Galtianhm. 207 

It would then in this respect occupy the place of the layer 
of varnish of the condenser. What however could, according 
to the view that the developed electricity depends on che- 
mical action (which can least of all take place at the sur- 
faces of contact), hinder the transference of the condensed op- 
posed electricities into one another, and allow of the con- 
densation even taking place ? Neither can it be a layer of air 
or of oxide placed between the two, since this must for the 
same reason oppose itself to the separation of the two elec- 
tricities; further, such a layer must then also appear as a 
hindrance to the transfer to the electrometer, where the at- 
traction for the opposed electricity does not even support the 
transition. In the mean time De la Rive has mentioned se- 
veral experiments, which were to prove in a direct manner, 
that contact, without contemporaneous chemical action, was 
incapable of developing electricity. We will at present follow 
him in these experiments. 

2. Already, some time ago, De la Rive had published some 
experiments, which he now again brings in support of his 
view {Recherch., p. 57), according to which the signs of elec- 
tricity, produced by two plates in contact in common air, no 
longer appear in a vacuum and in dried air. Nevertheless it 
is evident from the manner in which he performed these ex- 
periments, that their negative result is rather owing to his 
having connected the condenser made use of with the earth, 
by means of perfectly dried wood : now every one may con- 
vince himself that even in performing this experiment in com- 
mon air the condenser under these circumstances refuses its 
services. Besides, PfafF has already previously refuted these 
experiments experimentally, and with regard to further ob- 
servations on this point I may refer to p. 20 of his work. 

3. De la Rive, previously, in another place, and lately in 
his Recherch.f p. 60, has made the following experiment of 
importance. 

" A piece of potassium or sodium was fixed in a solid manner 
by one of its ends to a platinum forceps, while the other extremity 
was held by means of a wooden forceps, or what was better, an 
ivory one. If, after having well brightened it, it is surrounded 
by very pure oil of naphtha, [steinbr\ and the condenser be 
touched with the end of the platinum forceps, no electrical sign 
is observable ; while if the naphtha oil is taken off" and none re- 
main adhering to the metal, this is observed to oxidate rapidly 
by the contact of the air, and the electricity indicated by the 
electroscope is of the most lively kind. The condenser is 
scarcely necessary to render it perceptible. If sometimes 
some indications of electricity are obtained when the potassium 



208 G. Th. Fechner's Justification of the 

or sodium is in the oil of naphtha, then a small quantity of 
humidity has been introduced into the liquid, which had re- 
mained adhering to the surfaces of the two metals, and which 
exercises on them a chemical action which it is easy to recog- 
nise. Immersed in azote and in hydrogen the two metals still 
gave rise to a development of electricity proceeding from the 
action exerted upon them either by the gases, or by the 
aqueous vapour, from which it is impossible entirely to free 
them (?) ; and in proof of this chemical action, we see their 
surfaces lose their metallic brightness and become tarnished 
very much as would have taken place in the air." 

The result which I would draw from a repetition of this 
experiment is this ; that in the form adopted by De la Rive, 
it is altogether unfit to give a proof of the one or the other 
view, because potassium brought into connexion with the earth 
by means of dried wood, does not allow us to perceive either 
out of or in petroleum, [steinol] any development of electricity, 
which, according to both views, is explicable from the pro- 
perty of the condenser ; but brought into connexion with it, 
by means of moist wood, it immediately produces, both in and 
out of the petroleum, powerful action, which the supporter of 
the chemical view can explain from the chemical action pro- 
duced through the moisture, the supporter of the voltaic 
theory, from the increased conducting power of the wood ; of 
the influence of which in this case sufficient evidence is con- 
tained in the following details. The experiment, however, 
may be, in fact, so varied, that it becomes decisive, and in 
this form it speaks, as will be seen, against the chemica. 
theory. The following is the detail of the experiments. 

A potassium ball was furnished at two opposite points with 
fresh surfaces of section : into one surface was inserted the 
end of a platinum wire, into the other the end of an air-dried 
bar of wood, so that the ball was situated between both ; now 
the highly sensible condenser (at times brass, at times copper) 
which was connected with the electroscope with a dry pile 
described by me in these Annals, was brought into contact 
with the platinum, while the wood was held in the hand. I 
could perceive by the well-known manipulation with the con- 
denser either no, or very inconsiderable, traces of electricity. 
I then substituted for the wood a cut chip of a quill, and ob- 
tained the same result. If on the contrary. I held the potas- 
sium ball in the hand, and brought the condenser into con- 
tact with the platinum, I obtained a divergence of the gold- 
leaf, of remarkable strength*, without comparison much more 

* This was even the case when the potassium ball was not cleansed 
from the adherent petroleum ; and I cannot in the least from my experi- 



Contact Theory of Galvanism. 209 

powerful than we are accustomed to obtain with zinc; this 
is therefore well adapted to serve as an experiment of demon- 
stration in lectures. The same was the case if I held the 
bar of wood after slightly moistening it; and in the latter case, 
it was quite indifferent for the production of the effect, whether 
the ball was immersed in petroleum or not. I must therefore 
suppose, that De la Rive, since he obtained a result out of 
the petroleum, but none when the ball was in it, produced the 
conducting connexion with the earth through wood or ivory 
only within the petroleum, but when out of the petroleum by 
a more humid conductor ; otherwise there would be a direct 
contradiction between his and my observations. One may 
easily believe, since this contradiction did not escape me, that 
I frequently repeated and varied the form of this experiment, 
in order to convince myself that on repeating it in various 
ways, right would remain on my side. 

It remained now to observe, whether the absence of di- 
vergence by the use of air-dried wood was owing to the want 
of conducting power of the wood, or to the want of chemical 
action : for it could not indeed be denied, that, if the po- 
tassium ball was held with the hands or by means of a moist 
bar of wood, their moisture must act chemically upon it, 
which also, when the experiment is performed under petro- 
leum, may easily be recognised by the bubbles of gas rising 
from the point of insertion of the slightly moistened wooden 
bar. The following experiment, more direct than all which 
De la Rive cites in support of his views, proves quite decidedly 
that the bad conducting power of the air-dried wood alone at 
least suffices to explain the negative result. If I moistened 
one half of the bar which stood in connexion with the po- 
tassium, and also the point of insertion in the potassium, just 
as in the former experiments in which I obtained a result, 
but held the wood during the contact of the condenser with 
the platinum by the half which remained air-dried, I obtained 
the former negative result ; nay, this was even then the case, 
if while thus manipulating I moistened the potassium during 
the contact of the condenser with acidulated water, so that a 
kind of explosive, chemical action took place. By this then 
the insufficient conducting power of air-dried wood for such 
experiments is sufficiently proved, and every one may easily, 
and even without potassium, convince himself by substituting 
zinc for that metal, when the phsenomena take place in quite 

ments concur in the view of Ohm and PfafF, that an isolated intermediate 
layer of petroleum acted a part in De la Rive's experiments. 

Fhil, Mag. S. 3. Vol. 13. No. 81. Sept. 1838. P 



210 G.Th. Fechner's Justification of the 

the same manner if the same arrangement be observed. We 
see therefore that De la Rive's experiment, in petroleum, ac- 
cording to his account of it, could not succeed, either according 
to the chemical theory, or according to the voltaic theory, and 
that when it is all taken together, he proves nothing what- 
ever. I succeeded however in varying these experiments so 
that an argument may be drawn from them against the che- 
mical theory. 

From the extreme vivacity with which the divergence took 
place when the potassium attached to the condenser by means 
of a platinum wire or even by direct contact (for in effect the 
platinum is in this case quite unnecessary) stood in connection 
with the earth by a moist conductor, and from the excessive 
sensitiveness of the electrometer with a dry pile which I em- 
ployed, it appeared to me not improbable, that even without 
a condenser, by the contact of a negative metal with po- 
tassium, a divergence would take place. If the brass point 
from which the gold-leaf was suspended was brought into 
contact either directly, or even with the interposition of an 
air-dried strip of paper or linen, which appeared to conduct 
much better than air-dried wood, with the platinum wire 
of the potassium ball, whilst the latter was held immedi- 
ately with the hand or by a slightly moistened slip of wood, 
there might be perceived, when the gold-leaf had a certain 
stability, a very weak, but undeniabjle, negative electrical di- 
vergence ; and also a positive electrical one, if by reversing 
the combination I held with my fingers the platinum wire, 
and brought the electrometer with the intermediation of the 
air-dried inter-conducter, or even only a layer of oxide which 
had formed on the potassium, into contact with that metal. 
From the numerous and varied experiments, sometimes bring- 
ing the electrometer into contact with insulated, then uninsu- 
lated platinum, 'without the agency of potassium^ I became 
convinced, that in fact no divergence of the electrometer 
would be produced by such contacts ; the contact of the po- 
tassium was necessary ; similar counter-experiments have not 
been neglected in the following. 

From the distinctness of the signs obtained (which as yet 
do not afford any objection against the chemical theory) it 
appeared to me not impossible, even by the entire insulation 
of the potassium, to render signs of electricity perceptible, 
and thus entirely to do away with the influence of moisture. 
Under these circumstances, the condenser, for known reasons, 
cannot be made use of; on the other hand, it is true that this 
difficulty stood opposed even to the resultofthe application of an 



Contact Theory of Galvanism.. 211 

electrometrical apparatus constructed on different principles, 
namely, that the intensity of the electricity of two heterogeneous 
plates in contact is in the inverse ratio of the magnitude of their 
surfaces or magnitude of conduction; consequently, if the super- 
ficies of the electrometer be considerably larger than that of the 
potassium, and moreover the former be not well insulated, 
no result can be expected. In effect I could no longer ob- 
tain those signs of electricity which I had previously recog- 
nised with such complete certainty, if 1 held the potassium 
in a dry insulating forceps and touched my electrometer with 
the platinum wire of the potassium. I completely succeeded, 
however, even with this fine experiment in the following 
manner. I had an electrometer purposely made with the 
smallest surface possible, consisting solely of a very thin and 
short brass wire, which, as the axis of a surrounding gum 
lac cylinder, traversed the perforated bottom of an inverted 
drinking-glass, and from which within the glass was suspended 
between the pole plates of the pile of the electrometer a very 
small gold-leaf, 24 inches long, while the electricity could be 
transferred to the prominent end of the brass without the 
glass. Into the potassium ball was inserted a thin platinum 
wire, as short as the convenience of transfer of the electricity 
allowed, and the ball itself, for the purpose of increasing 
its surface, was pressed between two copper plates which 
had been soaked in petroleum, as smooth as was possible 
without cutting the potassium ball with the platinum wire. 
Thus the entire electrometer might have been somewhat about 
double the size of the surfaces of the potassium*. 

With this arrangement I now repeated the former experi- 
ments in the air, holding at times the potassium with the in- 
sulating forceps, at times the platinum, while the other metal 
was each time brought into connexion with the electroscope. 
If clear, opposite divergence of the gold-leaf could in this 
case be observed with the most complete certainty ; for this 
arrangement, if the combination of potassium and platinum 
was not insulated, proved to be much more sensitive than the 
one previously employed, and gave without the condenser the 
most evident divergences, (opposite by the opposite arrange- 
ment,) which might easily be increased up to the striking of 
the gold-leaf against the pole plates, if these were merely se- 
parated so far from one another (7^ lin.) as was necessary for 
the stability of the gold-leaf. 1 now placed the potassium 

* I endeavoured to unite several balls of potassium by pressure, but did 
not succeed, either from the petroleum which remained attached to them, 
or from the oxide which immediately formed at the surfaces of the fresh 
sections. 

P2 



212 G. Th. Fechner's Justification of the 

disc with the upwards bent wire, proceeding from it, in a 
small glass, covered it with petroleum up to about half an 
inch high, and discharged the platinum wire which projected 
from the petroleum (and which nowhere touched the glass) 
on to the electrometer, while I held the glass in my hand. 
The divergence to the side, 'which indicates the negative electri- 
city, followed in this case quite as constantly, evidently, and cer- 
tainly as if the potassium had been insulated in the air. I have 
already mentioned that the counter experiments in this case 
were not neglected. 

The following modes appear to me still to offer themselves 
for the explanation of the result of this experiment according 
to the chemical theory: 

a. Some moisture was brought together with the potassium 
into the petroleum, the chemical action of which caused the 
result. 

b. The petroleum was perhaps adulterated and still capable 
of acting chemically on the potassium. 

With respect to a. this objection has at first sight the ap- 
pearance of some weight, since it is true that when the po- 
tassium is brought from the air into the petroleum, we observe 
during some time a few gas bubbles rise up from the potassium, 
which undoubtedly are produced by the chemical action of 
the adhering moisture. But this development of gas soon 
ceases ; and long after this had entirely disappeared, twenty- 
four hours afterwards, during which time the potassium con- 
tinually remained immersed in the petroleum, (I did not ob- 
serve it for more than twenty-four hours afterwards) I have 
obtained the electrical signs in the petroleum of quite the same 
force, as during the development of gas and even in the air ; so 
that this objection thus completely falls to the ground. 

As to the objection b, the petroleum employed was that in 
which the potassium had already been preserved for many 
years without becoming anything more than deprived of its 
lustre at its surfaces ; while if the petroleum had contained 
any oxygen, this must necessarily have produced a gradual 
destruction of the potassium ; and even if the oil had in the 
beginning contained any oxygen, this would certainly have 
been consumed during the long preservation of the potassium 
in it, so that I conceive this second objection also to be com- 
pletely refuted. 

4. An experiment on which De la Rive appears to lay 
particular stress, since he refers to it in several places, is the 
following {Recherch., p. 67.) : 

" I took two zinc plates exactly similar with regard to 
their dimensions to the brass plates of an ordinary condenser ; 



Contact Theory of Galvanism. 213 

I soldered to each a brass knob {bout de laiton) ; I covered 
their inner surface with a thin layer of lac varnish, so that 
they might perform the office of the plates of a condenser ; 
I further entirely covered the exterior surface of one of the 
zinc plates with a layer of the same varnish, so that this plate 
was not in immediate contact with the air at any of its points. 
Various experiments were made, forming the condenser some- 
times with the two zinc plates, sometimes with one of them 
only and with a brass plate. When the zinc plate which I 
employed was that the entire surface of which was covered 
with varnish, I constantly obtained electrical signs much less 
strong than in employing that one of which the exterior sur- 
face was entirely uncovered and exposed to the immediate 
contact of the air. Presuming that the electricity, very feeble 
it is true, which was developed with the varnished zinc plate, 
arose from the circumstance that the layer with which it was 
covered was too thin to intercept completely all chemical action 
of the air and of the humidity, I successively increased the 
thickness of this layer, and I succeeded in rendering it such 
that the plate ceased to give any electrical signs. What 
moreover proves that it is to the action, even through the 
varnish, which the moist air could exercise upon the surface 
of the zinc, that the production of the electricity was owing, 
was that I observed after a short time a commencement of 
oxidation take place on this surface. We see, therefore, that 
when a zinc plate, by means of a layer of varnish, is entirely 
protected from the action of the air or of those agents which 
might exert a chemical action upon it, it does not become 
electric in its contact with a brass knob. Still more ; this in- 
active apparatus conducts itself as a homogeneous plate of 
brass. Thus on touching the brass knob which was soldered 
to the surface of the zinc, with the copper of a heterogeneous 
plate, of which I held the zinc in my hand, I succeeded in 
charging it with negative electricity. Or, according to the 
contact theory, the two coppers being in immediate contact, 
and placed between the two zincs soldered to them, viz. that 
of the condenser and that which I held in my hand, no re- 
sult ought to have taken place. We might obtain a result of 
the same kind, perhaps, still more striking, by uniting for the 
purpose of forming the conducter the two plates of zinc and 
making the two brass knobs soldered to them communicate 
with one another. In the theory of contact, the opposition of 
these two pairs, perfectly similar, ought to have neutralized 
all kind of action ; however, the experiment showed that the 
zinc plate, the naked surface of which was exposed to the air, 
became charged with positive electricity, while that of which the 



214 G. Th. Fechner's Justification of the 

surface was covered with a thick layer of varnish became nega- 
tive, just as a brass plate would have become in the same case." 
These experiments struck me in a very high degree, and 
1 have repeated them quite according to the method mentioned 
by De la Rive, with all the care which I considered to be due 
to experiments, which, accordingly as their result might turn 
out, would really testify for or against the chemical theory. 
But the issue was simply this ; that the results, after the var- 
nishing over of the zinc condenser, to which was soldered a 
copper knob, and after the varnish had become completely 
dry, were not perceptibly distinguishable from those which I 
obtained by over varnishing with the same condenser, although 
the layer of lac varnish with which I had covered by often 
repeated coatings the entire non-condensing'surfacesof the zinc 
condenser (while the condensing surface could only retain their 
thin coating of varnish, as was the case in De la Rive's ex- 
periments according to an express statement of his in another 
place) was laid on excessively thick, and with the most an- 
xious care that no point of the zinc might be left free. To 
go a step further still than De la Rive, 1 fixed, in order to 
lay aside the objection which perhaps might be raised re- 
specting the chemical action of the air upon the copper, a 
platinum wire to the copper point, and now varnished over 
even the whole copper point, so that platinum alone re- 
mained free. If the platinum was now touched with the finger 
or with a slip of paper which had been moistened in distilled 
water, the zinc condensers became quite as well charged with 
positive electricity as if it had not been varnished. Besides 
we are already in possession of some experiments ofBecquerel 
and Peltier (vide Becquerel's Traite, ii. p. 139) which have 
given a result similar to my own. However, in Becquerel's 
a small part of the zinc instead of being varnished was merely 
covered by glass, which De la Rive does not consider as being 
sufficient. In Peltier's experiments this circumstance was 
avoided; but the action of his apparatus, which was arranged 
in a different manner, I have not been able fully to compre- 
hend. But also in Pfaff', I find (vide his work, p. 22.) that 
he had repeated De la Rive's experiment quite in accordance 
with his own statement and had always observed the same ac- 
tion of the zinc condensers with varnish as without varnish. 

Moreover I have succeeded in deciding affirmatively the 
question, whether varnished zinc in connection with electro- 
negative metals developes electricity in a way by far more 
simple than by means of the condenser. 

By the application oi' an electrometer, quite similar to the 
one described under No. 3, except that is has a longer gold- 



Contact Theory of Galvanism. 215 

leaf (4^ Parisian inches), and instead of a brass point passing 
through the lac, one of gold, I obtain with a zinc plate 
to which a platinum wire is fastened, a constant divergence 
of the gold-leaf to the right or left, very small, it is true, 
but yet subject to no deception, accordingly as I connected 
the one or the other metal with the gold wire, while I held 
the other in the hand ; only by the connexion of the zinc 
with the gold wire the interposition of a moist conducter is, 
for reasons easily understood, necessary ; but not so, if I con- 
nected the platinum with it. For the latter case only I have 
employed unvarnished zinc, as also coated with a thick layer 
of varnish (so that even the point of connexion of the zinc 
with the platinum was carefully covered with it), and in both 
cases I obtained results not differing in any perceptible de- 
gree (namely, a remarkable equally strong negative diver- 
gence). The size of the zinc plate was such that the sur- 
face of the electrometer was inconsiderable in comparison 
with it. For the success of this experiment the pole plates 
must be placed as close as is compatible with the stability of 
the gold-leaf. 

5. De la Rive makes of importance [Recherch., p. QQ) that 
Becquerel by means of sensitive apparatus, according to the 
method which I have called the second in my paper in the 
Annals f vol. xli. p. 226, with the application ofa gilt condenser 
could, however, not demonstrate the slightest trace of electri- 
city between gold and platinum {Ann. de Chim. et Phys.^ xlvi. 
p. 292, or Traite de VElectr., t. ii. p. 137), and attributes this 
to the want of the chemical action of the air upon both metals ; 
while in fact, experiments with the multiplier, by the applica- 
tion of a fluid which would attack these metals, show that 
their combination is capable of exciting electricity. To this 
we may answer, that a multiplier only moderately sensitive 
is without comparison a more sensitive instrument for the de- 
monstration of the weakest traces of electricity than the most 
sensitive condenser ; therefore, by the undeniable only very 
weak electromotive oppositions of the gold and platinum, for 
which their chemical state itself speaks, it is very evident 
that the one instrument still indicates an action where the 
other would appear to show that none whatever takes place. 
Besides, the experiment of Becquerel completely loses all 
weight, for this reason ; that he found in the same experimental 
series, that graphite and some other bodies, on which no 
chemical influence of the air can be proved, are capable of a 
development of electricity with gold, plainly recognisable with 
the condenser, even after they had previously been washed 
in distilled water ; and I myself have already formerly men- 



216 G. Th. Fechner*s Justification of the Contact Theory. 

tioned the development of electricity between gold and silver, 
which may be demonstrated in a weak degree even without 
a condenser. If, indeed, De la Rive even in all these cases 
supposes (supponirt) a chemical action, I have only to observe, 
that it must also be allowed me to suppose in all cases an 
electrical action, where it cannot be demonstrated, where 
further it agrees better with the contact theory. 

6. Biot long ago convinced himself that piles constructed 
of an equal number of pairs of plates, with fluids of very dif- 
ferent chemical action, as water, solution of common salt, of 
sal ammonia, of chloride of potassium, of sulphate of iron, in- 
dicated at the electrometer the same intensity of the poles. 
If other fluids, such as solution of soda, showed exceptions 
(which become explicable according to the theory of contact 
by a change of the metallic surface), these are certainly not 
of the kind that can speak in favour of the chemical theory. 
De la Rive himself performed similar experiments {Recherch., 
p. 142) and found that piles constructed of an equal number 
of plates with river water, solution of Glauber's salts and greatly 
diluted nitric acid, indicated an equal power of electricity at 
the insulated pole, where (as was also the case in Biot's ex- 
periments) the other pole stood in connexion with the ground ; 
if on the other hand both poles are insulated, a difference 
occurs, and the diluted nitric acid gives the weakest, often 
quite imperceptible electrical signs. 

In order now to explain the equality of power, (for the first 
appearance is evidently opposed to the chemical theory) by 
construction of the pile with different fluids (in the case of 
non-insulation) De la Rive supposes that there is, it is true, 
more electricity developed by the liquids which attack more 
strongly, but that always one part of the developed opposite 
electricities reunites even through the members of the pile. 
But since fluids of stronger chemical action possess in general 
also a better conducting power, they would allow of a quicker 
reunion, and with this would be explained how the free portion 
of electricity is not stronger with them than with fluids which 
act less powerfully. Disregarding however other objections 
which might easily be raised against this view, it were yet 
very curious, if this compensation in the various fluids should 
amount exactly to the equality of the actions, and the more 
so, since the conducting power of the fluid members of the 
pile also depends in some degree on their dimensions ; conse- 
quently the compensation could only be exact with one single 
thickness of the fluid layers. With the theory of contact the 
equality of the intensity of non- insulated piles in the con- 
struction with various fluids (in so far as they do not charge 



Mr. Graves on Cubic Equations. 217 

their metallic surfaces) proceeds as a natural consequence 
without the aid of any hypotheses. The various action of the 
insulated pile is still enigmatic, but might possibly depend on 
this, that with a bad conducting fluid the amount of conduc- 
tion of the pile becomes greater, since then the electricity 
probably penetrates even between fluid and metallic surface, 
which might be less the case if the conducting power of the 
fluid approached more to that of the metal ; a subject more- 
over on which special experiments are still desirable. 
[To be continued.] 



I 



XXVIII. A New and General Solution of' Cubic Equations. 

By John T. Graves, of the Inner Temple^ Esq., M.A.* 
N the ordinary books of algebra, (so far, at least, as my 

limited acquaintance with them extends,) where cubic equa- 
tions are discussed, the cases o^ real coefiicients only are con- 
sidered, and different methods of solution are given in order 
to effect the separation between the constituentsf of the roots 
in different cases. I have obtained a symmetrical solution 
of the equation 

^H(x+ v'^rA)a; + i«'+'v/^v = (1.) 

which presents the constituents of x in an explicit form in all 
cases. This is all that is wanted, for the solution of a cubic 
equation of the general form. 

(«i+ >/=i /3i)y + («2+ v^ /32)y+ («3+ v=i ^s)2/ 

+ a4+'/-l/S4 = (2.) 

may easily be made to depend on the solution of a cubic 
equation of the form (1.) ; and, from the nature of the rela- 
tion between the transformed equation (1.) and the original 
equation (2.), the constituents (x, A, jw., v) of the transformed 
coefficients (x + a/— 1 A, jU-4- V— 1") are easily determinable, 
supposing the constituents of the original coefficients to be 
explicitly given : and if the constituents of x be determinable, 
those of 7/ can easily be determined. 

The limits of this Magazine do not permit an exposition 
of my process, which I intend hereafter to communicate at 
length through some more appropriate medium. It consists 
in an analysis of the following formula for x. 

where p — x+V— 1^ and q = /x 4-^—1 h and where the 

• Communicated by the Author. 

t I call ec and /3 the " constituents" of the expression et + a/—\ /3. 



218 



Mr. Graves on Cubic Equations. 



ambiguous p^ may have either of its two values, provided it 
retain at any one time the same meaning in both places of its 
occurrence in formula (3.). 

My resuli is presented in the following formulae, in which 
V' and ^ denote real roots not negative : coSg"^ denotes the 
smallest cos"^ not negative : and i denotes any term of the 
arithmetical series — 2, — 1, 0, 1, 2, reckoned from inde- 
finitely backward and forward. 



Let 



Qi = -^^^Vpc^+A^+x~ 



(4.) 






I 

Rl = ^J=f[ ^Qs + Q'4+ V'Q3-Q4)cOs|-L (2ix + COSo-l Q5) I 

R, = -^( J^'Q7+Q4- V'Q^Q4 ) sin 4' X(^^^+*^0«0~^QOT 



■(70 



(8.) 



5i = 2Qi^(xiOt + Av) +A(xv-An;^)^ 

52 = 2Q/(jciM, + Av)--A(jcv-X|*) [ 

53 = 2 Qi^ (jc V -X jOt) - A (x /x + A v) 
5^ = 2 Q/ (x V — A fi) + A (x )«, + A v) 

X = V^ + a/'^ Vq 



Then 



^1 n R j_ ^2 ^Q^Rj 



^^= v1?^^''^^77. 



(9.) 
(10.) 

(11.) 



From the preceding formulae it would be easy, did the size 
of the page permit, to write out at full length a solution for x 
in immediate terms of x, A, ju,, v. The relations infer se of the 
mediate functions employed are very remarkable. It will be 
seen that Sj, ^g, % and s^ are wanted merely as sigti-indicafors. 
The critical cases where a sign-indicator becomes = 0, are ira- 



Prof. Graham's Note on the Constitution of Salts. 219 

portant. It is also interesting to consider the conditions that 
are necessary in order that a root should be wholly real or 
wholly imaginary; and to observe the curious manner in 
which, when X and v are both = 0, the solution here given 
identifies itself respectively, according to certain relations be- 
tween X and /*, with the ordinary algebraical or trigonometri- 
cal solution. 

XXIX. Note on the Constitution of Salts. By Professor 
T. Graham *. 

T^HE author may perhaps be excused in drawing the at- 
-*- tention of chemists to a distinction in saline combina- 
tions, which is at present too often overlooked, and confusion 
thereby occasioned. The orders of monobasic, bibasic, and 
tribasic salts, of which the phosphates proved types, have 
lately been greatly enlarged by the discoveries of Liebig and 
Dumas respecting vegetable acids, and the distinctive charac- 
ters of these orders are well understood. The best proof of 
an acid's being bibasic or tribasic, is its combining at once 
with two bases which are isomorphous, or belong to the same 
natural family, as phosphoric acid does with soda and ammo- 
nia in microcosmic salt, and tartaric acid with potash and soda 
in Rochelle salt. Water and magnesia, water and barytes, 
water and oxide of lead, are also constantly associated as bases * 
in bibasic and tribasic salts, but never in true double salts, or 
combinations of two or more salts with each other, with which 
salts of the preceding orders are apt to be confounded. 

But it is too generally supposed, that a metallic oxide can- 
not exist in a saline combination, except in the capacity of 
base, although in most of those bodies which are at present 
termed subsalts, the whole or a portion of the metallic oxide 
is certainly not basic, but is attached to a really neutral salt 
in a capacity similar to that of constitutional water, or water 
of crystallization. Oxide of copper, oxide of lead, barytes, 
and the other metallic oxides included in or related to the mag- 
nesian family, appear to rival water (which is a member of the 
same family), in the frequency with which they discharge this 
function in the constitution of saline compounds, particularly 
of those belonging to the organic kingdom. Thus the neutral 
organic principle orcine combines with five atoms of oxide of 
lead, according to Dumas, which replace five atoms of water 
which orcine otherwise possesses. But it should be brought 
prominently into view, that neither the water nor the oxide of 

• Read before the Chemical Section of the British Association, at the 
late meeting at Newcastle, Aug. 22, 1838; and now communicated by the 
Author. 



220 Prof. Graham's Note on the Constitution of Salts, 

Jead is basic in these compounds, but superadded to the orcine 
like constitutional water ; a distinction which is well expressed 
in their formulae, by placing the symbols for water and oxide 
of lead after and not before that of orcine, or in the proper 
place for water of crystallization in the formula of a salt. 

Potash, soda, oxide of silver, and oxide of ammonium, on 
the other hand, are never found in this relation to a salt, or 
discharging any other function than that of base to an acid. 
Hence there are no such compounds as subsalts of these bases. 

In Peligot's late admirable paper on the varieties of sugar, 
[Annales de Chimie, &c., t. 67. p. 113 *), he has formed the 
compounds of that principle with barytes, lime, oxide of lead, 
and common salt, and determined their composition with great 
accuracy. Like preceding chemists he considers these com- 
pounds as salts, in which sugar is the acid and the metallic 
oxide the base, and continues to speak of them as saccharates, 
although with an evident reserve. But the conclusion is b}' 
no means necessary that sugar is an acid, and that the lime, 
oxide of lead, &c. are basic to it. On the contrary, sugar 
being a body neutral to test paper, is more likely to be a salt 
than an acid. That the metallic oxide attached to it discharges 
the function of the superadded water of crystallization of 
so many bodies, appears to me evident from the following cir- 
cumstances. 

1. It is separated from the sugar by the weakest acids, even 
by carbonic acid. 

2. It replaces water in the sugar, which water can also be 
replaced in part by an equivalent proportion of chloride of 
sodium, or by the hydrates of barytes and lime. Now basic 
water is never replaced by a salt, although constitutional water 
frequently is. 

3. But the circumstance which is decisive of the lime and 
oxide of lead not being basic in the sugar compounds is, that 
analogous compounds do not exist, containing potash or any 
of the strong alkaline bases of its class. No acid is known 
which forms a salt with lime or lead, that does not also form 
a salt with potash or soda ; but these last, as has been stated, 
are never present in any other capacity than that of bases, and 
are thus disqualified from replacing the water or magnesian 
oxide in combination with sugar. 

The test of the non-hasic character of laater or a metallic 
oxide in a compou7id^ is the absefice of a parallel combination 
containing an oxide of the potash class. 

The fact that the combined water in sugar is strongly at- 
tached and cannot be removed by heat, is no proof that the 

* A notice of M. Peligot's researches on this subject will be found in the 
present Number, p. 237.-'Edit. 



Notices respecting New Books: Rara Mathematica, &c. 221 

water is basic; for many nitrates, hyposulphites, &c., are 
known, the constitutional or superadded water of which can- 
not be removedby the same agency without destroying thesalts. 



XXX. Notices respecting New Books. 

A Brief Account of the Life, Writings, and Inventions of Sib. Samuel 
MoRLAND, Master of Mechanics to Charles the Second. 

Kara Mathematica ; or, A Collection of Treatises on the Mathe- 
matics and subjects connected with them, from ancient inedited ma- 
nuscripts. No. I. — Deightons, Cambridge ; Parker, London. 

THESE two works are anonymous ; but they carry with them 
sufficient evidence of a close intimacy with the subjects to 
which they relate. 

The little attention paid by Englishmen to the history of science 
in England is not a new subject of reproach. Almost every human 
pursuit has had its history investigated, its fragments published, 
and its cultivators biographed, except science : perhaps this class 
of researches requiring a combination of knowledge and tastes that 
rarely go together, may be the chief cause. There is so little seem- 
ing, so little real, fraternity between the taste for decyphering an- 
cient manuscripts, and that for pure scientific investigation, that we 
hail this class of publications as a real boon to the reputation of 
England. 

Of the first of these works, it will be unnecessary to say more 
than that it is a succinct history of the life of a man of great powers 
of mind, whose life was marked by the usual vicissitudes of the fol- 
lowers of a court in perilous times, and who was reduced at the 
end of his career to penury. Attached to this, is a short and inter- 
esting discussion of some points connected with the early history of 
arithmetic. 

The Rara Mathematica, No. 1. contains : — 

1. Sacro-Bosco de Arte Numerandi. 

2. A Method used in England in the Fifteenth Century for taking 
the Altitude of a Steeple or inaccessible object. 

3. A Treatise on the Numeration of Algorism; from a MS. of the 
fourteenth century. 

4. William Bourne on Optic Glasses; written about 1580. 

5. Johannes Robyns de Cometis. 

We think it unnecessary to say one word concerning the historical 
value of these tracts, as their importance will be at once admitted. 
We shall, however, on a future occasion give an analysis of them, 
and of such others as may appear in subsequent numbers ; but we 
may here express our anticipation of their furnishing materials for a 
decision upon some important points connected with scientific history, 
which have been, as yet, but very vaguely discussed. 

Finally, a work like this may safely repose upon its own intrinsic 
value, without any recommendation of ours ; and we have therefore 
merely felt it necessary to call the attention of our readers to its ex- 



222 Royal Society. 

istence. The chief objects to be kept in view are, the historical im- 
portance of the tracts selected for publication, and carefully decy- 
phering the doubtful contractions that occur in MSS. of the period 
which this collection is intended to include. The present number 
being taken as a specimen, we are sure the execution is in good 
hands. 



XXXI. Proceedings of Learned Societies. 

ROYAL SOCIETY. 
[Continued from p. 152.] 

May 31. — A paper was read, entitled, " Remarks on the Theory 
of the Dispersion of Light, as connected with Polarization." By the 
Rev. Baden Powell, M.A., F.R.S., Savilian Professor of Geometr)'' 
in the University of Oxford. 

The present paper is a sequel to those already presented by the 
author to the Royal Society, in which he had instituted a compari- 
son of the observations of the refractive indices for the standard rays 
of light in various media, with the results calculated from theoretical 
formulae, deduced from the most improved views of the undulatory 
hypothesis ; the cases discussed including the greatest range of 
data as yet furnished by experiment. The comparison exhibited an 
accordance sufficient to warrant the conclusion that the theory af- 
fords a very satisfactory approximation, at least, to the expression 
and explanation of the actual law of nature *. In order, however, to 
remove any possible discrepancy which may still exist, or hereafter 
be found to obtain, the author considers that further examination is 
requisite of the principles on which any extension or modification of 
the theory might be pursued ; and such is the object of the investi- 
gation undertaken in the present paper. 

The phenomena of interference, on which the undulatory theory 
was originally based by Dr. Young, obliged us to adopt some idea 
of an alternating motion, as well as a motion of translation, in our 
conception of light ; and this, with all the accessions it has received, 
especially from the investigation of Fresnel, has, at the present day, 
been connected by the labours of M. Cauchy and others, with gene- 
ral dynamical principles, which regulate the propagation of vibratory 
motions through an elastic medium. From such dynamical prin- 
ciples there have been deduced certain differential equations of mo- 
tion, the integration of which gives the well-known expression for a 
wave, involving the relation between the velocity and the wave- 
length which explains the dispersion. The direct and complete in- 
tegration of these forms, effected by M. Cauchy f, and simplified by 

* A notice of Prof. Powell's last 'paper on the subject was given in 
vol. xii. p. 367.; where also will be found references to abstracts of the 
three former. — Edit. 

t Prof. Powell's " Abstract of the Essential Principles of M. Cauchy's 
View of the Undulatory Theory," appeared in Lond. and Edinb. Phil. Mag. 
vol. vi. p. 16. etseq. 



Rev. Prof. Powell on the Dispersion of Light. '2'2S 

Mr. Tovey* and M. Kellandf, involves certain conditions; namely, 
the evanescence of certain terms, the interpretation of which implies 
peculiar views of the constitution of the ether, Mr. Tovey shows 
that without these conditions, a certain form of the wave-function 
is a particular solution of the equations ; and this form is precisely 
that expressing elliptically polarized light. If the absence of the 
condition in question be essential to the case of elliptically and cir- 
cularly polarized light, it follows that all the preceding investiga- 
tions, which depend on the fulfilment of those conditions, are ap- 
plicable only to unpolarized and plane-polarized light, and conse- 
quently the general integration is limited in a most material part of 
its application ; a defect which is only remedied by the supplement- 
ary investigation of Mr. Tovey, in which, for this case, a particular 
solution is assigned. It seemed, then, necessary to show explicitly 
that the non-fulfilment of the conditions, that is, the non-evanes- 
cence of the terms in question, is essential for elliptically polarized 
light, as their evanescence is for common light, and thus to exhibit 
distinctly the relation between the cases of elliptically polarized, of 
plane-polarized, and unpolarized light ; and, again, to remove, if 
possible, the obscurity and discrepancy of opinion in which the phy- 
sical interpretation of those conditions, with regard to the supposed 
constitution of the ethereal medium, appeared to be involved. 

The author then enters upon the analytical investigation of the 
subject, and in conclusion remarks that when light is elliptically or 
circularly polarized, that is, when any one of the two component 
vibrations is retarded behind the other, then, in the differential equa- 
tions of motion, the opposite terms do not destroy each other in the 
summation, which they can only do in general by supposing a great 
number taken into account ; that is, the number of terms is limited, 
or the sphere of the influence of the force by which the vibrations 
are propagated is small. When light is plane-polarized,- or unpo- 
larized, that is, when there is no retardation, or the phases of the 
component vibrations are simultaneous, then the opposite sums de- 
stroy each other; that is, the number of terms involved is greater, 
or the sphere of the influence of the force greater. Since both kinds 
of light can be propagated indifferently through ordinary media, it 
follows that the sphere of influence of the force, or number of mole- 
cules taken into account, does not here depend on the arrangement 
of the molecules of ether in the medium, but on the retardation of 
one of the vibrations behind the other, or the absence of it, origin* 
ally impressed on the ray in the respective cases. 

A paper was also read, entitled, "An Experimental Inquiry into the 
influence of Nitrogen on the Growth of Plants." By Robert Rigg, 
Esq. Communicated by the Rev. J. B. Reade, M.A., F.R.S., &c. 

The author, after briefly alluding to a former paper laid before the 
Royal Society, describing the chemical changes which occur during 

* Mr. Tovey's investigations on this subject have appeared, exclusively, 
we believe, in this Journal : see Lond. and Edinb. Phil. Mag., vol. viii. p. 7-j 
270, 500.; vol. ix. p. 420.; xi. 524.; and xii. p. 10, 259. 

f Prof. Kelland's development of his views will be foundin vol. x. p. 336. 



224- Royal Society. 

the germination of seeds, and some of the decompositions of vege- 
table matter, proceeds, in the present paper, to trace a connexion 
between the phenomena exhibited during the growth of plants, and 
the direct agency of nitrogen. The experiments by which the au- 
thor supports his views are arranged in separate tables, so drawn out 
as to indicate not only the quantities of carbon, oxygen, hydrogen, 
nitrogen, and residual matter, in about 120 different vegetable 
substances, but also the quantity of nitrogen in each compound, 
when compared with 1000 parts by weight of carbon in the same 
substance. The most important of these tables are those which ex- 
hibit the chemical constitution of the germs, cotyledons and rootlets 
of seeds; the elements of the roots and trunks of trees, and the cha- 
racters of the various parts of plants, especially of the leaves, at dif- 
ferent periods of their growth. From this extensive series, which is 
stated to form but a small portion of the experiments made by the 
author in this department of chemical research, it appears that ni- 
trogen and residual matter are invariably the most abundant in those 
parts of plants which perform the most important offices in vege- 
table physiology ; and hence the author is disposed to infer, that 
nitrogen (being the element which more than any other is perma- 
nent in its character) when coupled with residual matter, is the 
moving agent, acting under the living principle of the plant, and 
moulding into shape the other elements. The method of ultimate 
analysis adopted by the author, enables him, as he conceives, to de- 
tect very minute errors, and therefore to speak with certainty as to 
the accuracy and value of every experiment*. , 

A paper was also read, entitled, " Researches in Rotatory Mo- 
tion." By A. Bell, Esq. Communicated by the Rev. W. Whewell, 
M.A., F.R.S., &c. 

This paper, which is altogether analytical, contains several new 
theorems in rotatory motion, respecting the effect of the centrifugal 
force arising from a rotation about any axis, in producing rotation 
about another, inclined at any angle to the former ; and also a new, 
and comparatively concise, demonstration of the equations of the 
motion of rotation of a solid body, its centre of gravity being fixed, 
and the body being acted on by any forces. 

June 14. — A paper was read, entitled, " Researches on Suppu- 
ration ; " by George Gulliver, Esq., Assistant Surgeon to the Royal 
Regiment of Horse Guards. Communicated by John Davy, M.D., 
F.R.S,, Assistant Inspector of Army Hospitals.f 

A paper was also in part read, entitled, " Researches on the 
Tides," Ninth Series ; by the Rev. W. Whewell, M.A., F.R.S., 
&c. 

BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 
The Eighth Meeting of the British Association took place at 
Newcastle-upon-Tyne, in the week from the 20liii to the 25th of 

• An abstract of Mr. Rigg's paper on the germination of seeds will be 
found in Lond. and Edinb. Phil. Mag. vol. ix. p. 536 : see also vol. xii. 
p. 31, 232. 

t This paper will be found, entire, in the present number, p, 193. 



British Association — Geological Society. 225 

August ; the General Committee having met for the first time on 
Saturday, August 18th, on which occasion the chair was taken by 
Prof. Whe well, V.P., in the absence of the Earl of Burlington, Pre- 
sident ; and the Rev. J. Yates, the Secretary to the Council, read 
the report of the proceedings of that body for the past year. The 
first general meeting assembled in the Central Exchange on the 
Monday evening, August 20th, more than 3200 persons being pre- 
sent, when Prof. Whewell resigned the chair to the Duke of Nor- 
thumberland, the new President, and Mr. Murchison, the General 
Secretary, read his report, giving, agreeably to the directions of the 
Council, " a general and comprehensive view of the past progress 
and future prospects" of the Association. The several Sections 
were presided over by the following men of science : Section A, 
Mathematical and Physical Science, Sir John F. W. Herschel, 
Bart. ; B, Chemistry and Mineralogy, the Rev. W. Whewell ; 
C, Geology and Geography, President for Geology C. Lyell, Esq., 
President for Geography Lord Prudhoe ; D, Zoology and Botany, 
Sir W. Jardine, Bart. ; E, Medical Science, Dr. Headlam ; F, Sta- 
tistics, Col. Sykes ; G, Mechanical Science, Charles Babbage, Esq. 
The continued progress of the Association was evinced by the num- 
ber of tickets issued for members, which, up to the Wednesday 
evening, was 2350, being upwards of 500 more than the number at 
the close of the meeting at Liverpool last year. A paper read before 
Section B, appears in our present number, p. 219. 



GEOLOGICAL SOCIETY. 
(Continued from vol. xii. p. 592.) 

April 4. — A paper was read entitled, "A Description of Viscoimt 
Cole's specimen of Plesiosaurus macro cephalus, (Conybeare's)," by 
Richard Owen, Esq., F.G.S., Hunterian Professor in the College of 
Surgeons, London ; an abstract of which will be found in the " Pro- 
ceedings" of the Society, No. 57, and also in the Annals of Natural 
History for September. 

April 25. — A paper was first read, entitled, "Notes on a small patch 
of Silurian Rocks to the west of Abergele, on the north coast of Den- 
bighshire ;" by J. E. Bowman, Esq., and communicated by R. L 
Murchison, Esq., V.P.G.S. 

The author's attention was first directed to these strata by Mr. John 
Price, of New College, Bristol. They occur immediately south of 
the narrow belt of carboniferous limestone, which skirts the coast from 
the Great Ormes Head, eastward, to the Point of Air and the Estuary 
of the Dee. The belt of limestone is here not above a mile broad, 
and the strata dip N. or N.E. At the base of the limestone precipices 
at Craig y Forwyn, is a seam of impure coal about a foot thick, and a 
thinner layer of bituminous shale with carbonized impressions of Le- 
pidodendra ? and a leaf-like Poacites. The beds constituting the 
following section are successively displayed between Llandulas and 
Garthewin, a distance of nearly six mUes : — 

1. Immediately under the limestone is a conglomerate, the basis 
consisting of " light loam," and the rounded pebbles of 
Phil. Mag. S. 3. Vol. 13. No. 81. Sept. 1838. Q 



226 Geological Society. 

greenish, slightly micaceous sandstone, containing a few bi- 
valves and joints of encrinites. This stratum the author has 
also seen between Llandeilo Bay and Colwyn on the Holyhead 
road, but the pebbles are there sometimes a foot in diameter. 

2. Thin bed of the same sandstone. 

3. A thick deposit of red marl, containing numerous angular and 

water-worn pebbles, interspersed thickly with shells appa- 
rently belonging to the Ludlow rocks. This marl forms a 
considerable part of Ffernant Dingle ; but it alternates with 
a compact marl, and is sometimes speckled green or yellow. 
The beds dip at a high angle to the north. Similar pebbles 
are found on the top of the limestone precipices, and beyond 
them on the beach, 

4. Compact, hard, arenaceous conglomerate, composed of pebbles 

more or less rounded, of liver-coloured and green micaceous 
shelly sandstone, also of pebbles of quartz, and the reddish 
subjacent limestone. 

5. Thin beds of compact reddish limestone containing few organic 

remains. It passes occasionally into a calcareous sandstone. 

6. Near the lower end of the dingle, the limestone rests on a bed 

of very fine blue clay. 

7 . Blue clay-slate, finely grained, slightly micaceous, and containing 

occasionally a layer of small shells. It sometimes presents 
obscure indications of vertical cleavage. This rock constitutes 
the whole of the southern portion of the dingle, and in one 
place is traversed by a fault. 
The rill in Ffernant Dingle flows into Melin y Person brook. The 
red marly conglomerate is there succeeded, on the south, by alluvium 
containing slate pebbles. Above the village of Bettws Abergele the 
slate rocks occur, but are greatly contorted; and on the height a little 
further south, and to the east of the road, is a hard finely grained rock 
inclosing joints of small encrinites. Still further south this rock alter- 
nates with beds of breccia, containing encrinital and other organic 
remains, the imbedded angular fragments consisting of glossy clay- 
slate. A little south of this quarry, towards Garthewin, the non- 
fissile blue slate again occurs, and the author found in it abundance 
of small fragments of encrinites, with univalves and bivalves. These 
fossils occurred apparently in layers, but were much decomposed. 
Similar remains were noticed, by Mr. Bowman, in the debris of the 
lead mines at the Bronhaylog, to the north-east of Garthewin. 

The paperwas accompanied byalistof fossils prepared by Mr. James 
de Carle Sowerby, including the following species which have been 
foundby Mr.Murchison in the Ludlow Rocks elsewhere : Lepteenalata, 
Terebratula nucula, T. pulchra, T. navicula, Conularia quadrisulcata, 
Atrypa affinis, Orthis orbicularis, Cypricardia cymbaformis, var., Nu- 
cula ovalis, Euomphalus funatus, Orthoceras striatum, Avicula re- 
troflexa, and Pleurotoma corallii. 

A notice "On the Occurrence of Wealden strata at Linksfield, near 
Elgin ; on the Remains of Fishes in the Old Red Sandstone of that 
neighbourhood ; and on raised beaches along the adjacent coast ;" by 
J. Malcolmson, Esq., F.G.S., was then read. 



Geological Society, 227 

The country around Elgin is composed of sandstones, conglome- 
rates, and concretionary limestones, belonging to the old red sand- 
stone ; but at Linksfield, one mile south of Elgin, that formation is 
overlaid, unconformably, by a series of beds, which Mr. Malcolmson 
has ascertained, by their organic remains, to represent the Wealden 
strata of England, though they have been usually considered to be 
lias. 

The following section gives the principal beds in descending order, 
the average thickness of the whole series being from 20 to 30 feet : 

1. Blue clay, containing thin bands of limestone, the lower being 

shelly. 

2. Thin bands of limestone and clay. 

3. Blackish shale, not bituminous, 1 to 2 feet. 

4. Compact grey limestone, without shells, in layers separated by 

clay, 4 feet. 

5. Laminated green clay, with a network of fibrous carbonate of 

lime. 

6. Red, sandy, calcareous marl, abounding with rolled pebbles of 

granite, gneiss, &c., also angular fragments of the fine- 
grained yellow and grey sandstone forming the hills to the 
west, but the geological position of which is not yet ascer- 
tained. 
Cornstone of the old red sandstone in unconformable position. 
The fossils are principally found in the lower bands of the top bed. 
They are rarely well preserved, and cannot be separated from the 
rock. The species are few in number, but abundant in individuals ; 
and one species of Cyclas is undistinguishable from the C. media of 
Sussex, found also by Prof. Sedgwick and Mr. Murchison in the 
Isle of Skye : there is likewise an Avicula, which agrees with one 
found in the Purbeck strata at Swanwich. Mr. Malcolmson procured 
also fragments of an Astarte and a Venus, and a microscopic univalve. 
The clay below this shelly limestone is full of the valves of a new, 
round species of Cypris. The author also obtained teeth and scales 
of fishes ; and the Rev. G. Gordon has found a Saurian bone. 

Fossils of the same description have been recently discovered by 
that gentleman at Lhanbryde, three miles to the east of Linksfield ; 
and in a micaceous white sandstone, he has procured a large Pinna, 
which Mr. James Sowerby has identified with a species found in the 
Portland sand of England. In April, 1832, Mr. Gordon communi- 
cated to the Society a notice of the discovery in a dark clay*, pene- 
trated while draining the Lake of Spynie, of the Turritella muricata of 
the Coral Rag. Mr. Malcolmson, therefore, hopes that many members 
of the series above the old red sandstone, not yet known to exist south 
of the Murray Frith, will be discovered by the practical geologists 
resident in that district. 

Mr. Martin, of the Anderson Institution, has recently discovered 
in a bed of calciferous conglomerate, near Elgin, and supposed by 
Mr. Gordon to represent the old red sandstone of Clasbennie in 

• Proceedings, vol. i. p. 394 j or Lend, and Edinb. Phil. Mag. vol. i, 

p. 227. 

Q2 



228 Geological Society. 

Perthshire, scales, teeth, and bones of fishes ; and, by comparing these 
remains with a magnificent specimen of a fish from Clasbennie, in Mr. 
Murchison's possession, Mr. Malcolmson has ascertained this suppo- 
sition to be correct. A doubt, therefore, which formerly existed re- 
specting the age of the conglomerate, is now removed. 

The paper concluded with an account of eleven ancient beaches on 
the coast, rising above each other, and from one of which, 15 feet 
above high- water mark, and cut through in draining Loch Spynie, 
Mr. Malcolmson procured twelve species of existing marine tes- 
tacea. 

A paper, " On the Origin of the Limestones of Devonshire," by 
Robert Alfred Cloyne Austen, Esq., F.G.S., was afterwards read. 

The object of the paper is not to account for the origin of calca- 
reous matter, or the means by which marine animals derive it from 
the surrounding medium, but to show how far the limestones of 
South Devonshire may have been produced by polypi. 

These limestones are stated by the author to occur, in nearly every 
instance, in the immediate vicinity of volcanic disturbances, and to 
be partly included in the slates and sandstones, and partly to rest 
upon them. To the former belong the broad band extending from 
Staple Hill to Dean Prior, the minor bands in the neighbourhood of 
Hempstone and Totness, and all those which occur beyond the Dart ; 
also the limestones of Newton and Torbay. They are said to be 
less pure and more slaty than the overlying limestones, and to be 
frequently separated by seams of shale. Transverse sections of these 
bands show, that the strata in some cases become thinner as they 
descend, and that the partings of shale increase, as near Staverton 
in the vaUey of the Dart, and at Staple Hill ; but that in other in- 
stances, as between Newton and Totness, the strata instead of fining 
off end abruptly upon the slate, and are covered in the direction of 
the dip by similar slates. The strata are always inclined, but they 
invariably form a table-land at the surface. This inclined position 
the author conceives is not due to dislocation, but to the beds having 
been deposited at the angle which they now present ; and he illu- 
strated his opinion, by a section between three and four miles in length, 
through the parishes of Pegwell, Denbury, and Abbots Kerswell, a 
remarkably level country. The bands of limestone dip 40°, but are 
nowhere more than 150 feet thick, and they all contain the same de- 
scription of organic remains. If the bands were deposited horizon- 
tally, and the most recent nearly at a level with the surface of the 
ancient ocean, then the lower beds, the author says, would have been 
placed at a depth of nearly three miles, although the organic remains 
prove that all the beds were formed under precisely similar condi- 
tions. 

In the structure of the Devonshire limestones, however, Mr. Austen 
considers that he has discovered evidences of an origin similar to that 
of modem coral reefs, and which will explain their inclined position. 
At Ogwell Park the limestone forms a horizontal capping to the in- 
clined strata; and at Bradley rests conformably against a ridge of slate 
the basset edge of each bed rising to the level of the crest of the ridge. 



Geological Society. 229 

This structure, Mr. Austen states, agrees with that of the coral reefs 
in the Southern Ocean, where the polypi raise their habitations on the 
flat summits or sides of submarine hills, to a level with the surface of the 
water. The stratified arrangement of the calcareous masses he consi- 
ders may be explained by the occasional deposition of sedimentary mat- 
ter, which might interrupt, for a time, the labours of the polypus ; and 
thus a series of beds would be produced varying in thickness accord- 
ing to the recurrence, at shorter or longer intervals, of interfering 
agents, each bed rising successively to the surface level of the water. 
If the deposition of sedimentary matter were great, then the polypi 
would be destroyed, and the reef would become encased in a mecha- 
nical accumulation. In further proof of the limestone of Devonshire 
having been coral reefs, Mr. Austen adduced the great abundance of 
zoophytes found on the surface of the lower strata, imbedded in the 
layers of sand which separate the beds ; and, he added, that their 
absence in other parts, especially in the interior of the bands, is no 
objection to his view of the origin of the limestone, because, in re- 
cent reefs, all traces of organic structure are frequently obliterated. 

May 9. — A communication by Dr. Black, F.G.S., was first read, 
" On a fossil stem of a Tree recently discovered near Bolton-le- 
Moor." 

The rock in which this fossil was found, occurs in the middle of the 
coal-measures, about 50 yards beneath a six-feet bed of coal, and it 
rests upon another bed four feet thick. It consists of three strata of 
argillaceous sandstone dipping from 15° to 18° to the south-west, and 
amounting in all to about 40 feet in thickness. The upper portion of the 
fossil stem was discovered about thirty feet beneath the surface of the 
rock, and the lower end extended to within 5 or 10 feet of the 
subjacent bed of coal. It was inclined 18° to north-east, or in an 
opposite direction to the sandstone strata ; and, when first laid open, 
it appears to have been about 30 feet in length, but at the time it 
was examined by Dr. Black only 12 feet remained in situ. The 
upper end of this portion was 15 inches in diameter, and the lower 
9 inches. The whole of the exterior of the stem was singularly 
striated, and irregularly furrowed, as if by compression ; and it was 
coated with a layer of coal, which evidently occupied the place of the 
bark. The interior of the stem is stated to be composed of a dark, 
hard, argillo-ferruginous sandstone, having a specific gravity of 2'9. 
A Stembergia, about an inch in diameter, extended along the whole 
length of the stem, and in some parts appeared to be half imbedded 
in a groove in it. This connexion of the two plants was Dr. Black's 
principal object in making the communication to the Society, not 
having previously observed a similar occurrence, nor having heard 
that it had been noticed elsewhere by other collectors. He is of 
opinion that the Stembergia was not accidentally allocated wdth the 
larger stem, but that it was, while living, a parasite, and in this 
respect resembled the mighty creepers of the existing tropical 
regions. 

A paper was next read, " On the Distribution of Organic Remains 
in part of the Oolitic Series on the coast of Yorkshire;" by Mr. 
Williamson, Curator of the Natural History Society of Manchester. 



230 Geological Society. 

In former communications* Mr .Williamson explained the vertical 
range of organic remains in the Lias and inferior and great oolites, and 
in this he showed their distribution in the upper sandstone and shale, 
the combrash, the Kelloway Rock, and the Oxford Clay. 

The upper sandstones and shales vary considerably in their characters, 
but they consist of three principal divisions, the highest and lowest 
being composed of sandstones sometimes ferruginous, and the middle 
one of clays and shales. The principal localities for the fossils are on 
the north side of Scalby Beck, near Scarborough, and Burniston Bay. 
The most characteristic plants are Pecopteris Murrayana, Cyclopteris 
digitata, and Otopteris obtusa ; but remains of Cycadese and Equiseta 
also occur. The list of plants is much smaller than that generally 
given, in consequence of Mr. Williamson having removed, to the great 
oolite, a bed generally considered as belonging to the upper sand- 
stones. 

Cornbrash. — This formation seldom exceeds live feet in thickness, 
and in Cayton Bay consists of the following strata in descending 
order : 

Fissile oolite 6 inches. 

Softer rock, sometimes ironshot. . 2 feet. 

Hard ironshot rock 2 feet. 

Blue clay, from 3 inches to 4 feet. 

The fossils contained in the fissile upper bed, are chiefly Terebra- 
tula ovoides, T. obsoleta, Ostrea edulina, and 0. Marshii. The greater 
portion of the organic remains are found towards the middle of the de- 
posit, the following being the most abundant : Ammonites Herveyi, 
Ostrea Marshii, Plagiostoma rigidulum, P. interstinctum, Trigonia 
clavata, T. costata, Cardium citrinoideum, Unio peregrinus, Amphidesma 
decurtatum, A. securiforme, My a literata, and Clypeus orbicularis. 
Twenty other species also occur, but less numerously. In the bed of 
clay, remains of a small Astacus (?) are obtained, also a shell resem- 
bling an Unio, and an undescribed Belemnite. Thirteen of the species 
found in the cornbrash are stated to exist also in the great oolite of 
Yorkshire, and nine in the coralline or Oxford oolite. 

Kelloway Rock. — This deposit consists of soft sandstones, some- 
times calcareous, but towards the top it is occasionally very ferrugi- 
nous ; and it varies in thickness from 35 to 70 feet. The fossils are 
numerous and highly characteristic, particularly the Ammonites. 
The ferruginous bed is full of organic remains, consisting chiefly of 
Belemnites abbreviatus, B. tornatilis, Ammonites Calloviencis, A. sub- 
Itevis, A. Kbnigi, A. Sutherlandeee, Ostrea Marshii, Gryphea dila- 
tata, /3. The most abundant species in the sandstones are, Ammo- 
nites jlexicostatus , A. subleevis, A. gemmatus, A. Calloviencis, A. per- 
armatus, A. ichthyodorsus (W.), A. gamma (W.), A. rotifer (W.), 
A. oblisus (W.), Belemnites abbreviatus, B. tornatilis. Turbo sulcosto- 
mus, Terebratula ornithocephala, T. socialis, Gryphaa dilatata, Ostrea 
Marshii, Avicula Braamburiensis , A. expansa, Lucina lyrata, Amphi- 
desma recurvum : 1 8 other species of testacea occur, though less abun- 

* Proceedings, vol. ii., pp. 82, 429 ; or Lond. and Edinb. Phil. Mag. 
vol. v. p. 222., vol. X. p. 137. J Geol. Trans. Sec. Ser. vol. v. Part I., p. 223, 
et teq. 



Geological Society, 231 

dantly. Five species are stated to be common to the Kelloway rock 
and the combrash, and ten to the Kelloway rock And the coralline 
oolite. Remains of fishes and of Ichthyosauri and Plesiosauri also 
occur in the deposit. 

Oxford Clay. — ^This great argillaceous formation is about 130 feet 
thick, and consists chiefly of fissile shales, but towards the upper part 
it becomes sandy. Fossils are comparatively rare in it, and are con- 
fined to the lower part, the only shell discovered in the upper by Mr. 
Williamson being Pinna lanceolata. The characteristic fossils are 
Ammonites Vernoni, A. cristatus, A. athleta, A. occulatus, Belemnites 
gracilis, Nucula nuda, N. elliptica, Pinna mitis, Astarte lurida,A. ca- 
rinata, Avicula expansa. The bed resting on the Kelloway rock is 
characterised by Belemnites abbreviatus and Gryphaa bullata. 

In future communications, the author purposes to illustrate the 
distribution of organic remains in the higher oolitic strata of the 
Yorkshire coast, 

A paper was afterwards read, " On the State in which Animal 
Matter is usually found in Fossils ;" by Mr. Alfred Smee, Student 
of King's College, London, and communicated by Prof. Royle, M.D„ 
F.G.S. 

The author first describes briefly, the composition of those parts 
of recent animals capable of being preserved in a fossU state ; and 
then proceeds to detail his investigations into the composition of 
fossil organic remains. 

For the sake of arrangement, he divides fossils into two great 
classes, one in which animal matter is present in various states, the 
other in which it has been removed. The first class he further sub- 
divides into three cases : 1. comprehending those fossils in which 
animal matter retains its original condition ; 2. those in which it 
has been partially changed; 3. those in which only the carbon of 
the animal matter remains. 

1 . The following examples were given of the first case. 

Small portions of the tooth of a horse, of an ox, and a stag, from 
the chalk rubble at Brighton, were submitted to the action of diluted 
muriatic acid ; and after the earthy portions had been removed the 
animal matter retained the shape of the bone, was white, and of the 
consistence of cartilage. Fragments of a tooth of a mammoth from 
Norfolk, and of a rib of a mastodon from Big-bone-lick in Ohio, when 
similarly treated, gave the same results. A thin slice of the rib ex- 
hibited under the microscope the stinicture of recent bone. Frag- 
ments of a stag's rib and horn, of an ox's head, and the tusk of a 
boar found near the Bank of England, associated with Roman imple- 
ments, retained their animal matter unaltered. Small portions of a 
Terebratula and of tv/o species of Productse, from the Silurian rocks of 
Malvern, were placed in very diluted muriatic acid, and when the 
earthy portions had been removed, small flocculi of animal matter, re- 
sembling the recent membrane of a shell, floated in the solution. A 
minute fragment of Asaphus caudatus yielded little shreds of animal 
matter. The experiments on the shells were repeated several times 
with the same results. Under the microscope these fossils exhibited 
also the structure of recent shells. 



232 Geological Society. 

2. The second case, in which animal matter has been partially 
changed, was illustrated by the following experiments. Portions of 
a stag's jaw from the Brighton chalk rubble, of a fish-bone, and a 
shark's tooth from the London clay, when dissolved in diluted mu- 
riatic acid, gave only a brown powder ; and the animal matter of a 
fragment of the humerus of a mastodon from Big-bone-lick exhibited 
but little flexibility, and was easily torn, particularly in the longitu- 
dinal direction. It was found impossible to make sections of the 
jaw-bone of the stag or the humerus of the mastodon for microscopic 
observation. Part of a human parietal bone found upon the site of 
the cathedral of Old Sarum, and human bones obtained from the 
church-yard of St. Christopher le Stocks, on part of which the Bank 
of England stands, were ascertained to have had their animal matter 
reduced to the same state as that of the stag's jaw. A fossil oyster 
from the Isle of Wight, when placed under the microscope, showed 
black spots over its surface, and the structure of the shell was appa- 
rently destroyed. A fragment of a Pecten from the lias also exhi- 
bited opaque spots. Part of an ammonite when dissolved left a sub- 
stance resembling Sepia. 

3. The third case, where only the carbon of the animal matter 
remains, was explained by two series of experiments, one of which 
proved it to be associated with bitumen, and the other that it existed 
by itself. The scales of Dapedium politum and other fishes from 
Lyme Regis, when acted upon by acid, left carbon undissolved ; and 
when heated under a test-tube gave a considerable quantity of 
bitumen*. 

Portions of the bones of the Ichthyosaurus and Plesiosaurus from 
the lias, yielded a black residuum, which deflagrated with red hot 
nitre, and the resulting mass gave a precipitate with chloride of cal- 
cium. To prove that the carbon was a portion of the bone and not 
an adventitious ingredient, a section was made, and the greatest 
quantity of carbon was found in the thickest part ; and an analysis 
showed that the proportion of carbon was about the same as in the 
animal matter of a similar mass of recent bone. A still further proof 
was adduced, in no gelatine having been detected after 36 hours 
boiling of a fragment of the fossil. A section of recent bone dis- 
played, when carbonized by heat and charged with crystals of alum 
or a composition of whitening, a similar appearance in the arrange- 
ment of the carbon as in the fossil bone. No bitumen was given off", 
when fragments of these bones were acted upon by heat under a 
test-tube.* 

With respect to the second great class in which the animal matter 
has been removed, the following cases were mentioned : — Portion of 

* [We presume it is here intended to be implied, though it is not so 
stated, that the bitumen associated with the carbon in these fossil fish- 
scales is itself a part of the altered animal matter, in a state of imperfect 
carbonization. Such an inference would appear to be confirmed by the 
negative result obtained with the bones of the Ichthyosaurus and Plesio- 
saurus subsequently stated. See the observations of Mr. Murchison and 
Mr. Faraday on the origin of the bitumen in the bituminous schist cf See- 
feld, in Phil. Mag. and Annals, N.S., vol. yi. p. 39. — Edit.] 



Intelligence and Miscellaneous Articles. 233 

the external and internal parts of a mammoth tusk from Siberia, did 
not blacken by heat, and dissolved completely in muriatic acid. The 
internal part of a tusk from Ohio gave the same results, but the ex- 
ternal part was found to contain a considerable proportion of animal 
matter. Inbones from the crag, the animal matter had been abstracted. 
Human bones which had been long buried were found to be in the 
same state. 

The paper concluded with the following remarks. As the diiFerent 
states, in which animal matter is found in fossils, pass insensibly into 
each other, and as many of the changes occur in church-yard and other 
bones, it follows, that no extraordinary circumstances are requisite 
to produce these alterations ; but that they may be effected by the or- 
dinary processes of putrefaction. Even the carbonization of animal 
matter may be accomplished by similar processes without the aid of 
heat, as bones become black by being macerated too long. It is also 
to be observed, that the parts of animals preserved in the fossil state, 
are those which longest resist putrefaction. It having been likewise 
shown that the degree of change does not depend upon the age of 
the bed in which the fossil occurs, it is a curious subject of inquiry 
for the geologist to ascertain how far the conditions necessary to pu ■ 
trefaction, air, a certain temperature, and moisture, were present in 
those strata, in which the change has been great ; how far they were 
absent in those, in which the change has been small. 



XXXII. Intelligetice and Miscellaneous Articles. 

THE SWISS ASSOCIATION FOR THE ADVANCEMENT OF NATURAL 

SCIENCE. 

This Association will hold its Annual Meeting on the 12th, 13th, 
and 14th of this month at Bcile, that is to say, a few days after that 
of the French Geological Society at Purrentray in the Swiss Jura 
(which is about 14 leagues from B^le), and two days previous to 
the opening of the German Association at Fribourg in Baden (about 
12 leagues from B§,le). 



errors in the nomenclature of certain stars in 
groombridge's catalogue. 

The following notice has been inserted in the monthly notices 
of the Astronomical Society for March, at the request of the 
Astronomer Royal : we transfer it to our pages for the purpose of 
giving it further publicity. 

Immediately after sending out a number of copies of Groom- 
bridge's Catalogue, I discovered that some errors had been com- 
mitted in the nomenclature of the stars, with reference, chiefly, to 
their accordance with the corrections made by Mr.Baily in Flam- 
steed's British Catalogue. These errors arose from the omission of a 
comparison which was supposed to be fully included in another. 



234? Intelligence and Miscellaneous Articles. 

I have since made a collation ; and I think it probable that the fol- 
lowing list contains the whole of these errors. 

Groombridge, No. 462 and 463 constitute 59 Andromedae. 



1172 


is 


7 Lyncis. 


1297 and 1298 


are 


20 Lyncis. 


1478 is not 




7 Ursse Majoris. 


1984 is not 




22 CanumVenaticorum. 


2185 is 




8 Ursse Minoris. 


2780 is not 




19 Lyrse. 


3196 is not 




44 Cygni. 


3412 is not 




68 CygniorBradley2775. 


3427 is 




68 Cygni, Bradley 2775. 


4240 is 




Bradley 3216. 


4241 is 




Bradley 3217. 


March 9, 1838. 




G. B. Airy. 



ON THE CHEMICAL REACTIONS OF WATER. BY M. KUHLMAN. 

The influence exerted by the action of water in some chemical re- 
actions, has already been the subject of several important observa- 
tions. Proust has shown that nitric acid of sp. gr. 1*48 does not 
attack tin, and that by the addition of a little water its action is ex- 
tremely energetic. M. Pelouze has more recently stated some other 
facts: 1st. That acetic acid, of sp. gr. r063, does not decompose 
carbonate of barytes ; 2ndly. That the carbonates of potash, soda, 
lead, zinc, strontia, and magnesia, are decomposed by crystalli- 
zable acetic acid ; but that the energy of the action is greater when 
water is added, and that there is no action upon these carbonates 
when the acetic acid is mixed with absolute alcohol ; lastly. That 
anhydrous alcohol, sulphuric aether, and acetic aether, completely 
mask the properties of the most powerful acids ; their solutions 
do not redden litmus, and do not attack a great number of car- 
bonates. 

The rational explanation of so strange a fact (the non-action of 
acetic acid mixed with alcohol upon carbonate of potash) is not 
readily found. The intervention of insolubility, as likely to oppose 
the formation of acetate of potash, cannot be alleged; for this salt is 
not only soluble in alcohol, but is a mixture of alcohol and acetic acid. 

M. Braconnot has added other observations to these, especially 
with respect to nitric acid. This acid, concentrated and boiling, 
does not at all act upon fragments of marble, or carbonate of bary- 
tes in powder ; this non-action is attributed by him to the insolu- 
bility of the nitrates of lime and barytes in concentrated nitric acid, 
and to the affinity which retains the carbonic acid in its com- 
pounds. 

M. Braconnot has also determined, in a manner which is appa- 
rently satisfactory, that if neither tin, iron, lead, nor silver, are at- 
tacked by concentrated nitric acid, it is because the nitrates of these 
metals are insoluble in this acid. It is to the same cause that he 
attributes all the results obtained by M. Pelouze. 



Intelligence and Miscellaneous Articles. 235 



"tD 



The following new facts, which admit of the explanation of M. 
Braconnot in certEiin cases, cannot I think be generalized, and that 
other causes besides those mentioned oppose the action of acids upon 
bases or their carbonates. 

One of the most remarkable chemical reactions is that which re- 
sults from the contact of sulphuric acid with barytes. It is well 
known that this combination is sometimes effected with the extri- 
cation of so much heat, that the mass of barytes becomes red hot, 
and part of the sulphuric acid escapes in the state of vapour. I 
have found some peculiarities respecting this combination, which 
appear to me to possess some scientific interest. 

A . A fragment of barytes, put into contact with cold Nordhausen 
fuming sulphuric acid, occasioned immediate and very vivid action. 
This action was still more vivid when anhydrous sulpliuric acid, lique- 
fied at about 77° Fahr., was, employed. 

B. A fragment of barytes, recently calcined, put into cold sul- 
phuric acid, containing only one atom of water, of sp. gr. 1-848, 
suffered no alteration ; no appearance of combination occurred. 
After remaining some time in contact, action suddenly takes place 
when the mixture is exposed to moist air ; it may be also effected 
by slightly touching the barytes, moistened with sulphuric acid, 
with a hot iron, or a glass rod moistened with water. 

C. A fragment of barytes was put into contact with sulphuric 
acid of sp. gr. 1*848, to which a small quantity of water was pre- 
viously added, and incandescence was the immediate result. The 
action is equally speedy when weaker sulphuric acid is employed, 
but no incandescence occurs. 

D. Sulphuric acid of density r848, which did not act upon re- 
cently calcined barytes, acted energetically upon barytes which had 
absorbed a little moisture from the air. 

E. Hydrated sulphuric acid, properly diluted so as to act imme- 
diately on barytes, does not act when cold, if it is mixed with 
absolute alcohol or pjrroxilic spirit. 

From these different results, it may be inferred that hydrated sul- 
phuric acid, containing only one atom of water, is with difficulty 
separated from it ; it neutralizes in some mode the properties of the 
acid ; for even in the presence of so powerful a base as barj'^tes, the 
acid does not act without the assistance of heat.* 

It becomes very important to state exactly the density of sul- 
phuric acid, when it is employed in chemical reactions ; for by the 
experiments above detailed, it appears that this acid combines ener- 
getically with barytes, when put into contact with this base at com- 
mon temperatures, in the state of anhydrous acid, fuming acid, or 
when weaker than I" 84 8, but it ceases to act when it is exactly 
1-848. 

If the anhydrous acid, or the fuming acid of Nordhausen, did not 
combine with barytes very energetically, it might be inferred, in 
order to explain the necessity of weakening the acid of 1-848, that 
the formation of sulphate of barytes cannot occur under these cir- 

* See Prof. Graham's paper on water as a constituent of salts in Lond. 
and Edinb. Phil. Mag. vol. vi. p. 327.— Edit. 



236 Intelligence and Miscellaneous Articles. 

cumstances, except by the previous formation of hydrate of barytas 
at the expense of a part of the water feebly retained by the sul- 
phuric acid ; but the facts stated render this opinion inadmissible. 
When employing acid of r848 density, the heat, as well as the 
addition of a little water, occasions the reaction, and in the latter 
case, the presence of the water unquestionably does not intervene, 
except by the extrication of the requisite heat. This extrication 
may be owing to different causes ; in the experiment C, it may be 
attributed to the combination of a part of the water of the weak 
acid with barytes, or the formation of hydrate of barytes ; and in 
the experiment D, it is hydrate of barytes ready formed, which, be- 
ing more favourable to combination, gives immediate rise to the 
production of sulphate of barytes by its contact with sulphuric acid 
of density 1-848. 

The explanations given by M. Braconnot of the non- action, under 
certain circumstances, of the acids upon metals, their bases or car- 
bonates, are not, in the opinion of M. Lassaigne, applicable to the 
results of the experiments related ; they are equally unsatisfactory 
in explaining the phasnomena observed by Proust, and which relate 
to the action of nitric acid upon tin, — an action which gives rise to 
the production of a compound which is insoluble (stannic acid), even 
when the acid is in the state most favourable for energetic action. He 
is also of opinion that in all the reactions described by MM. Proust, 
Pelouze, and Braconnot, the great stability of the compounds of 
acids and water, when they exist in the proportions stated with re- 
spect to the weights of their atoms, exerts great influence ; and 
that the mixture of alcohol and aether with the acids results, not 
only from giving a liquid which is not susceptible of dissolving the 
product which may arise from the reaction of these acids on the bases 
or the carbonates, but from preventing all action from occurring by 
taking from the acids the portions of water which are not retained 
by stability of combination. The experiment E. gives support to 
this opinion. 

In the contact of nitric acids with the metals, the presence of a 
little uncombined water also undoubtedly intervenes to facilitate the 
reaction. Ammonia, the formation of which occurs with iron, zinc, 
and cadmium, as is the case with tin, favours this opinion ; but this 
influence cannot be readily admitted with respect to lead, copper, 
and sUver. 

In the course of these experiments, M. Lassaigne found that the 
action of nitric acid upon the metals is always accompanied with 
the formation of more or less ammonia, according as the metals de- 
compose water more or less readily. The metals which do not de- 
compose water yield no traces of ammonia. 

In operating upon potassium and sodium, nevertheless, he ob- 
tained no traces of nitrate of ammonia, which he attributes to the 
high temperature produced, and at which the nitrate of ammonia 
cannot exist : these experiments with the metals of the alkaline ox- 
ides are not free from danger, on account of the violent explosion 
which takes place at the moment of contact between them and the 
nitric acid. — Ann. de Chimie, Ixyii. 209. 



Intelligence and Miscellaneous Articles. 237 

ON SUGARS. BY M. PELIGOT.* 

Common Sugar. — On repeating the analysis with all possible care, 
the author found that the formula long since adopted is that which 
best agrees with experiment : this formula is C'-^ H'^'^ O " f. 

M. Berzelius found that the compound of sugar with oxide of lead, 
is C'^* H-o O '0, 2 Pb O. On drying this salt at 320° Fahr., M. Peligot 
obtained C'-^ H's O^, 2 PbO. Anhydrous sugar will therefore be C^* 
His O" instead of C^* W Oi". 

The author also obtained a crystallized saccharate of barytes, 
crystallized by the direct contact of sugar and barytes dissolved in 
water, and he found the formula to be C-* H— O", BaO ; he com- 
bined sugar with common salt, and found the composition of this 
body to be C+« H^"- O^', Ch"- Na. 

Sugar of Starch and of Diabetes. — The formula of these and of 
the grape and honey sugar, M. Peligot found to be C-^ H-^ O'*. He 
also analysed the compound of diabetic sugar and common salt 
obtained by Calloud, and found that this curious product is repre- 
sented by the formula C"**^ H^- O"^, Ch- Na ; the compound of sugar 
of starch and oxide of lead, obtained by the contact of ammoniacal 
acetate of lead and sugar dissolved in excess, was found to be C''^ H^'^ 
O^, 6 PbO ; the saccharate of barytes from sugar of starch is repre- 
sented by C« Ho6 028, 3 BaO. 

M. Peligot found that common sugar is the only one which com- 
bines with the alkalis without suffering change. Sugar of starch 
and all other known sugars, at first combine with the alkalis, and 
are gradually destroyed, giving rise to two distinct products, ac- 
cording to the circumstances of the mixture of these bodies. 

Lime dissolved in a solution of starch sugar, gradually loses its 
caustic property, and is saturated by an acid formed by its influence. 
The salt of lime formed, when rendered neutral, is abundantly pre- 
cipitated by subacetate of lead. The formula of the insoluble salt is 
C48 1130 015, 6 PbO. The disengaged acid could not be conveniently 
examined : it is not volatile, and forms salts, almost all of which 
are soluble in water. On heating the solution of starch sugar and 
an alkali, a more rapid action is observable ; the mixture becomes 
coloured, and a brownish-black acid is formed, having some resem- 
blance to ulmic acid, but it is quite distinct from it. Its composition 
is represented by the formula C^s H^oQ'o. It appears to be iden- 
tical with the acid obtained by M.Suanberg, in treating the acid of 
catechu with caustic potash, which has the composition represent- 
ed by the preceding formula ; nevertheless differences occur in the 
analyses, which indicated one per cent, too much hydrogen. This 
acid is very readily obtained with fused starch sugar, and a concen- 
trated solution of potash ; the action is rapid. When the colour has 
become very intense, water is added, and the acid is precipitated by 
hydrochloric acid. If it be identical with the japonic acid, this 
acid is represented by C^^^H'^ O^, These two acids differ from sugar 

• See Prof. Graham's paper, p. 219. of the present number.— Edit. 
f The original atomic weights are preserved. 



238 Intelligence and Miscellaneous Articles, 

only in being minus water : for, C^*^ H-'^ O'^^ anhydrous sugar, be- 
comes C+« H30 0'8, the first acid, by losing 6 H'^ O; then C's ffo O'^ 
becomes C*8 H^'' O^, japonic acid by losing 7 H- O. Sugar thus loses 
water successively even in the midst of water. This remarkable 
transformation is well characterized with starch sugar, and analo- 
gous sugars. When the sugar and alkali are not in contact with 
water, the phsenomena of decomposition no longer occur : an alkaline 
saccharate is obtained in which the sugar possesses its usual pro- 
perties. 

M. Peligot has examined the nature of the action of acids, and 
particularly that of concentrated sulphuric acid upon sugars. With 
sulphuric acid and common sugar, a deep colour is produced, and a 
certain quantity of japonic acid is formed. With sugar of starch, 
on the contrary, there is no colour ; and what is very remarkable 
is, that this sugar and the acid combine and form sulphosaccharic 
acid. This is to be saturated with carbonate of barytes, and treated 
with subacetate of lead : sulphosaccharate of lead is precipitated, 
the composition of which is C^s H'*" 0'-° SO^ + 4 PbO ; but it has 
not been precisely determined what quantity of water the sulpho- 
saccharic acid contains. This acid when uncombined is not very 
stable : it does not precipitate barytic salts, and in general forms 
soluble salts. 

The action of heat upon sugars, when properly managed, yields 
very simple results ; at about 410° Fahr., water only is obtained, and 
a black product remains, which is entirely soluble in water. The 
author has preserved the name of caramel for it. When purified by 
alcohol a tasteless substance is obtained, which does not ferment. Its 
composition is very simple, C*sH-''^Q'S; and it differs only from 
sugar in losing a part of its water. Common and starch sugar, 
treated in this way, both yield the same substance. 

These experiments, it will be seen, greatly modify the present 
opinions of the atomic weight of sugars, confirming the analyses 
already made of cane and starch sugar. 

Journal de Ch. Med. — June, 1838. 



SUCCISTERIN. 

MM. Pelletier and Walter, in examining the pyogenous products of 
amber, have obtained and analysed several substances, among which 
there is one that they think worthy of being particularly noticed. 

It is white, crystalline, scarcely soluble in alcohol or aether, and 
its colour is rendered intensely blue by sulphuric acid. The analysis 
which they have performed indicates the formula C^ H^ ; it has there- 
fore the same composition as idrialin, and possesses also all its pro- 
perties. It is well known that idrialin, which was discovered by M. 
Dumas, has been met with only in a mineral, the site of which is 
lost, and is found only in a few mineralogical collections. The 
authors do not assert the identity of idrialin with the substance 
which they have found in amber. If it be supposed that they are 
merely isomeric, they propose the name of succisterin for the newer 
compound. — L'Institut, Juin, 1838. 



Meteorological Observations. 



239 



Register of Meteorological Observations for June 1838, made at Applegarth 

Manse, Dumfries-shire. By the Rev. Wvi. Dunbar. 

(Omitted last Month.) 



Days 

of 

Month. 



Barometer. 



9 a.m. 9p.m 



9 a.m. 9 p.m. 



Therm. 



Wind. 



Rain. 



Weather. 



June 1 
2 

3 
4 
5 
6 
7 
O 8 
9 
10 

11 

12 
13 
14 

([15 
16 
17 
18 
19 
20 
21 
022 
23 
24 
25 
26 
27 
28 
29 

))30 



29-80 
29-63 
29-54 
29-49 
29-71 
29-96 
30-05 
30-13 
29-97 
29-48 
29-49 
29-61 
29-68 
29-51 
29-50 
29-53 
29-64 
29-55 
29-30 
29-49 
29-21 
29-37 
29-89 
29-80 

29-9 » 
29-86 
29-75 
29-80 
29-87 
29-70 



29-75 
29-58 
29-50 
29-60 
29-85 
30-02 
30-08 
30-11 
29-71 
29-40 
29-50 
29-67 
29-64 
29-50 
29-49 
29-55 
29-67 
29-36 
29-50 
29-20 
29-25 
29-60 
29-91 
29-80 
29-93 
29-86 
29-80 
29-85 
29-85 
29-74 



50 

49§ 

55 

59 

62 

61^ 

56 

55 

54 

50 

56 

55 

53 

51 

53 

55 

57 

60 

55i 

59 

57 

52 

60 

62 

56 

66 

56 

61 

54 

54§ 



49 

49 

52 

53 

52i 

47 

45^ 

48| 

50 

51 

49 

49^ 

51 

48 

53 

55i 

56 

57 

55 

50 

51 

52 

54§ 

56 

58 

50 
48i 
54 
56 



sw. 

ssw. 

s. 

s.w. 

E, by N< 

ssw. 

N. &S. 
SSW. 

s. 

SE. 
NE. 
NE. 
NE. 
SW. 

s. 
s.by w, 

N.E. 



SW. 

sw. 

ssw. 
ssw. 
ssw. 

SK. 
SE. 



NE, 

NE. 



1-12 

0-46 
0-72 



0-62 
1-80 
1-46 



0-96 
1-32 
3-74 



0-60 



Cold and withering. 

Fine : rain : genial. 

Showery and sunny. 

Showery and warm. 

Showery: thunder. 

Showery : cold p.m. 

Dry : cool : genial. 

Dry : cool : genial. 

Dry, but threatening rain 

Wet all day. 

Wet : thunder. 

Dry and pleasant. 

Dry : rather cool. 

Wet throughout. 

Very genial day. 

Soft rain all day. 

Fine growing weather. 

Fair A.M. : wet r.M. : thund. 

Wet preced^ night : dry p.m. 

Very wet afternoon. 

Fair all day. 

Showery a.m. : cleared. 

Fair : fine day. 

Fair all day. 

Fair and mild. 

Fair and warm. 

Wet A.M. : cleared up. 

Fine summer day. 

Showery, but warm. 

Cloudy and moist. 



Mean. 29-7I 29-67 56 Slfl 



7-26 



METEOROLOGICAL OBSERVATIONS FOR JULY 1838. 

Chiswick. — July 1. Cloudy and fine : rain. 2. Sultry : rain. 3. Rain. 4. Hazy: 
fine. 5. Very fine. 6. Heavy rain with thunder: fine. 7, 8. Fine. 9 — ll.Veryfine. 
12. Overcast. l.S. Very hot: lightning at night. 14. Rain. 15. Showery. 16 — 22. 
Very fine. 23. Overcast. 24, 25. Fine. 26. Cloudy and fine : rain. 27. Fine. 
28. Very fine : slight rain. 29. Cloudy: rain. 30. Heavy showers. 31 . Very fine. 

Boiton.— July 1. Cloudy : rain early a.m. 2. Cloudy : rain p.m. 3, 4. Cloudy. 
5. Fine. 6. Fine: rain p.m. 7. Fine. 8. Rain. 9. Cloudy. 10. Fine. 11. 
Cloudy: rain early a.m. : rain p.m. 12. Cloudy. 13. Fine : thunder and light- 
ning p.m. 14. Cloudy: rain early a.m. : rain p.m. 15. Fine: rain p.m. 16. 
Cloudy. 17. Fine. 18. Cloudy. 19. Fine. 20—22. Windy. 23. Fine: 
rain p.m. 24. Fine. 25. Cloudy. 26. Fine : rain p.m. 27. Stormy. 28. 
Fine. 29. Fine : rain a.m. SO. Fine : rain a.m. 31. Fine. 

Applegarth Manse, Dumfries-shire. — July 1. Shower a.m. : fair p.m. 2. Fair 
all day. 3, 4. Fine summer days. 5. Excellent weather. 6. Warm : thunder : 
rain. 7. Showery all day. 8. Fair : mild : cool p.m. 9. Dull day: very cloudy. 
10. Rain in the afternoon. 11. Rainy all day : fog p.m. 12. Rain : cleared up 
P.M. 13. Showery. 14. Showery all day. 15. Showery : cleared p.m. 16. 
Showery a.m. : cleared. 17. Wet all day. 18. Fine day : moist p.m. 19. 
Showery all day. 20. Fair day, though cool. 21. Fair a.m.: showery p.m. 
22. Fair throughout. 23. Heavy rain : thunder. 24. Fair throughout. 25. 
Fair, but cool. 26. Wet nearly all day. 27. Showery a.m. 28. Showery 
nearly all day. 29, 30. Showery v.m. 31. Fair throughout. 



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THE 

LONDON AND EDINBURGH 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



OCTOBER 1838. 



XXXIII. Remarlcson the Constitution of the Atmosphere; ad- 
dressed to Dr. Dalton, F.R.S., by John William Draper, 
M.D., Professor of Chemistry in Hampden Sydney College, 
Virginia, Member of Acad. Nat. So. Philad., S^c. ^^c* 

Hampden Sydney College, Virginia, U. States, 
Respected Sir, June 25, 1838. 

I HAVE this morning read, with much pleasure, the re- 
marks inserted by you in the Numbers of the London and 
Edinburgh Philosophical Magazine for February and May 
last, in relation to the constitution of the atmosphere, and other 
important points connected with investigations of its composi- 
tion. 

It fully appears, if we admit the hypothesis brought for- 
ward many years ago by you, and generally received by che- 
mists, that a gas acts as a vacuum to the particles of one of 
another kind, that the constitution of the atmosphere is not 
such as it ought to be. The hypothetical result, contrary to 
what is popularly imagined, would indicate a continuous vari- 
ation in the composition of air at different altitudes, and give 
us two limits, the one marking out an elevation beyond which 
oxygen could not be found, and the other the same for the 
azote. From a long experience in these matters, and a per- 
fect acquaintance with these theories, you have given it as 
your opinion, that in the higher regions of the air, the pro- 
portion of oxygen to azote is less than at the surface of the 
earth, but not nearly so much as the theory of mixed gases 
would require, and that the reasons for this must be found 
in the incessant agitation of the atmosphere from winds and 
other causes. 

In America, partly for the foregoing reason, and partly for 

* Communicated by the Author. 
Phil. Mag. S. 3. Vol. 13. No. 82. Oct. 1838, R 



242 Dr. J. W. Draper's Remarks on the 

others to which I will presently allude, some chemists have 
altogether rejected the hypothesis of gaseous action, perhaps 
on very insufficient grounds. It is therefore desirable that 
the subject should be more extensively investigated, and these 
objections set aside. No one can do this more ably than 
yourself. 

If a soap-bubble be expanded with hydrogen gas, in an at- 
mosphere of common air, and then be suddenly burst, so as 
to accomplish an instantaneous diffusion and intermixture, at 
the moment at which this occurs there is an expansion, which 
is apparently of a thermal kind, inasmuch as the gaseous 
mixture, in a short space of time, recedes to its original 
volume. One hundred measures of hydrogen and four hun- 
dred of atmospheric air occupy, on the moment of being 
mixed in this way, considerably more space than five hun- 
dred measures. Does not this indicate that the particles of 
these gases occupy, when their temperature has fallen to the 
original degree, a less space than the sum of their volumes 
before mixing ? Is it not a phaenomenon of the same kind 
as that observed on mixing alcohol and water, when there is 
a thermal disturbance, followed by a penetration of dimen- 
sions? In other words, does not this experiment give indi- 
cations of proof, that certain gases, on being simply mixed, 
exist in a condensed state ? 

This result is readily observed on mixing hydrogen with 
atmospheric air, and also with nitrogen gas. I detected it 
some years ago, but have not yet been able to show it in the 
case of other gases. If it be really due to a condensation 
taking place, it is an experiment of no ordinary importance ; 
especially if it should be found that the same occurs on 
mixing oxygen with nitrogen. It would indicate to us one 
of those " other causes" which keep up the integrity of the 
constitution of the atmosphere. 

One of the most powerful arguments brought forward in 
support of the hypothesis of gaseous action, is founded on the 
experiments of Professor Graham ; it is, that the law which 
regulates the flow of gases into a vacuum, is precisely the same 
as that which regulates their flow into each other: is this 
however strictly the case? 

Professor Graham has shown*, that when hydrogen gas, car- 
bonic acid, &c. are separated from atmospheric air by a thin 
screen of stucco, they diffuse themselves according to the law of 
the square roots of their density. One volume of air, for ex- 
ample, replaces 0*8091 of carbonic acid gas ; the gas therefore 
on that side of the screen where the carbonic acid was placed, 

[* See L. and E. Phil. Mag. vol. ii. p. 175 ; vol. iv. p. 321,] 



Constitution of the Atmosphere. 



243 



increases in quantity. But if any one will throw into a soap- 
bubble one hundred measures of carbonic acid, and expose it 
to atmospheric air, he will perceive a very different result to 
that just mentioned, for instead of gas accumulating within 
the bubble, a very extraordinary and rapid diminution will 
ensue: this phaenomenon is not a little remarkable; it does not 
require any instrumental arrangement to detect it. A bubble 
of carbonic acid gas an inch in diameter, collapses in the 
space of a few minutes to the size of a common pea. 

Again, if carbonic acid, &c. and atmospheric air are kept 
from directly mingling with each other, by being separated by 
a thin lamina of India-rubber, they will pass through the 
barrier to intermix. Do they intermix with a force greater 
than the pressure of one atmosphere ? Dr. Mitchell of Phila- 
delphia found that carbonic acid would pass through a piece 
of India-rubber, and diffuse itself into atmospheric air, though 
resisted by a pressure greater than two atmospheres (63 inches 
of mercury). This first cast doubts on the hypothesis of 
gaseous action, for if it can be proved that these mixtures 
are effected with a force greater than that which is measured 
by one atmosphere, the idea that gases act towards each other 
as vacua, necessarily falls to the ground. 

Allow me. Sir, to point out some experiments which seem 
to bear on this matter. Let us examine, for instance, whether 
sulphurous acid will pass into atmospheric 
air with a force greater than the pressure 
of one atmosphere. A tube of glass, about 
one third of an inch in bore, and ten inches 
long, is bent into a kind of siphon so that 
one leg shall be about six, and the other 
two inches long. The extremity a a, has 
a lip or rim turned on it, at the lamp; and 
in the longer leg a thin glass tube cc, about 
one eighth of an inch in bore, and closed at 
one extremity, is included to serve, as will 
be hereafter shown, as a gauge. Next, the 
extremity h of the siphon is closed, there 
being inserted through it two platinum 
wires dd, e e, parallel to each other, but 
not touching. The arrangement is thus 
completed for use. Let us suppose it is re- 
quired to pass through India-rubber, sul- 
phurous acid gas, into atmospheric air 
condensed by a pressure of five or six atmospheres; the long leg 
of the siphon is to be filled with water, which is excluded from 
the gauge tube c c, owing to its narrowness ; next, a strong de- 
coction of litmus is to be placed in the short legi until it is half 

R 2 




c 



\JJ 



244? Dr. J. W. Draper's Remarks o?i the 

filled. The rim round the extremity a a, is then daubed with a 
piece of burnt caoutchouc, and upon it is tied a thin piece of that 
substance, with a fine but strong waxed thread. Over this is se- 
cured a piece of stout silk or cotton cloth, for the purpose of 
fortifying the elastic barrier. The wires d d e e, are next made 
to communicate with the poles of an active voltaic battery, 
and the condensation commences ; for the gas which is evolved 
from these electrodes, rising to the top of the tube, accumu- 
lates there, causing the column of water in the short leg to 
rise and condense the atmospheric air above it. The mem- 
brane though fortified gives way to a certain extent, becoming 
convex outwards ; and as the accumulation of gas in the long 
leg continues, the condensation of that in the short one in- 
creases, as is indicated by the gauge cc. A very thin India- 
rubber, of the diameter here indicated, will stand a pressure 
of 6 to 20 atmospheres without rupture, if its silken support 
is good ; and I have found that anointing the edges of the 
rim with the burnt substance enables the operator to tie the 
barrier on so that no leakage can occur between it and the 
glass, under the severest pressures. When the gauge indicates 
that the required degree of condensation is arrived at, the 
connexion with the battery is broken, and the condensation 
of course stops : the siphon being carried to the mercurial 
trough, taking care to keep its position erect, its short limb 
is depressed under the mercury and carried into ajar contain- 
ing sulphurous acid. If, under these pressures, any of the 
acid gas finds its way into the condensed air, its presence is 
detected by the reddening of the blue litmus water. It is 
necessary here to observe, that the indications of the tube 
gauge do not give a correct estimate of the amount of con- 
densation, but always represent them higher than they are, 
according to Marriotte's law. It has long been known, that 
the volume of gas dissolved in water depends in a great mea- 
sure on the pressure exerted on it ; now it will be found, when 
the operation is conducted in an instrument arranged as this, 
that a certain proportion of the air in the gauge disappears 
in this manner. Its zero point is therefore altered, and the 
condensation appears higher than it really is. It may be re- 
marked, in passing, that it is surprising to see to what an 
extent the absorption of the oxygen and hydrogen is carried 
in the longer leg, owing to their making their appearance in 
the nascent form. To ascertain the true condensation, so 
soon as the passage of the sulphurous acid or other gas has 
taken place satisfactorily, the membrane is to be punctured 
with a pin ; and when a pneumatic equilibrium is attained, the 
height of the liquid in the gauge will mark the point where 
the zero of the scale should be placed. 



Constitution of the Atmosphere. 



245 



--/ 



In this way it may be shown, that sulphurous acid will pass 
instantaneously into atmospheric air, against a pressure equi- 
valent to two hundred and twenty inches of mercury, or seven 
atmospheres and a third. 

The curved form of the instrument just described was 
found to present certain inconveniences when pi-essures up- 
wards of 6 or 7 atmospheres were made use of. The volume 
of air, which at the beginning of the experiment occupied the 
greater part of the extent of the shorter limb, had now col- 
lapsed much in its dimensions, and owing to the unavoidable 
giving way of the India-rubber and silk cover, had retreated 
beneath it out of sight. It was not found expedient to lengthen 
this limb, for that entailed a corresponding increase in the 
dimensions of the battery, in order to produce a given con- 
densation in a given time. A straight tube was therefore 
taken, about three sevenths of an inch in bore, and a rim 
turned on it at a a ; at the closed extremity the 
platina wires b c entered ; a gauge tube d was 
dropped in between them; water was then 
poured to the height e e ; and lastly, a tube^, 
containing an appropriate chemical test, was 
inserted, its bottom resting on the top of the 
gauge tube. Nothing remained but to tie on 
the India-rubber with its silken support, and 
by the voltaic battery to proceed to condense. 
In this instrument the test fluid was never out 
of sight, nor did the volume of the gas suffer 
any inconvenient change ; the gauge too was 
well located for observation, and a given con- 
densation could be produced in less time, and 
by a less amount of electricity, than with the 
siphon tube. It is to be observed, however, that * ^ 

the gaseous matter evolved from the water mingles with the 
atmospheric air in the upper part of the tube, and therefore 
the passage of the gases tried, does not take place into at- 
mospheric air, but into a mixture of oxygen, hydrogen, and 
nitrogen. 

The tube f being filled with lime water, and a pressure 
amounting to ten atmospheres being produced in the vessel, 
it was exposed to an atmosphere of carbonic acid gas, at 
ordinary pressures. In this course of a few minutes, the upper 
part of the tube containing the lime-water began to look 
milky, and in an hour a cloud of particles of carbonate of 
lime had fallen to the bottom. 

Again, having filled the test tube f, with a solution of ace- 
tate of lead, and produced a pressure amounting to twelve 




a 



946 Dr. J. W. Draper's Remarks on the 

atmospheres, it was exposed to sulphuretted hydrogen. In a 
very short time the black sulphuret of lead appeared, giving 
tokens of the rapid passage of the gas. A comparative ex- 
periment was made, in order to discover whether the trans- 
mission took place more slowly than when it was resisted by 
such a severe pressure. It appeared, however, so far as the 
experiment could be tried under similar circumstances, as re- 
gards the thickness of the barrier, &c., that sulphuretted hy- 
drogen gas went through a barrier against a pressure of 
three hundred and sixty inches of mercury, to mix with another 
gas, as readily as if no force were exerted against it. 

As numerous experiments, which had been tried on various 
gases, had failed to indicate any obstacle to their passage, it be- 
came necessary to know whether at the most extreme pressures 
that could be commanded they would pass through a barrier. 
To accomplish this, I took a strong and narrow tube, and 
having turned a rim at one end, and sealed five platina wires 
into the other, \Jilled it with distilled water, and inclosed a 
narrow capillary tube in it, the gaseous contents of which 
were small. As a test, in the upper part of the arrangement, 
and in lieu of the tube f, I placed a slip of paper which had 
been alternately soaked in acetate of lead and carbonate of 
soda; the India-rubber was fortified by a piece of very strong 
silk, which was carefully tied on; there was not therefore any 
gaseous matter present, except the small quantity of air in 
the gauge tube. The condensation went on with great ra- 
pidity, a mixture of oxygen and hydrogen gradually accumu- 
lating in the top of the vessel, bulging out the India-rubber 
and silk barrier, until it was almost hemispherical. It was 
my intention to try a pressure of twenty-five atmospheres ; 
and when that was supposed to be reached, the instrument 
was immersed in sulphuretted hydrogen. Very soon the test 
paper became of a tawny yellow, and finally it was quite 
black ; the pressure when the experiment was over was de- 
termined to be twenty-four and a quarter atmospheres. 

At a temperature of 48° Fahr., and pressure 29*74< bar. 
sulphuretted hydrogen gas passes through a barrier into a 
mixture of oxygen and hydrogen, though it may be resisted 
by a pressure of twenty-four arid a quarter atmospheres, or 
nearly seven hundred and thirty inches of mercury. Like sul- 
phurous acid, it will become diffused into an atmosphere beyond 
it under a greater pressure than that which is sufficient to con- 
dense it into a liquid. 

These results would appear, at first sight, entirely opposed 
to the hypothesis of gaseous action, and important enough to 
cast doubts upon its correctness, if not entirely to destroy it. 



Constitution of the Atmosphere. 247 

To me, however, it seems that an explanation can be given of 
them, which will lead us entirely to a different conclusion, 
and furnish a beautiful illustration of the truth of that hypo- 
thesis. 

It appears there is abundant and conclusive evidence, that 
under ordinary circumstances of temperature and pressure, 
any given gas bears the same relation to one which is perco- 
lating into it that a vacuum would do, for the law of dis- 
charge is identically the same. For the purpose of illustration, 
we may therefore regard it to all intents as a vacuum, and 
reason accordingly. If the particles of heterogeneous gases 
possess no repulsive tendency as respects each other, but are 
perfectly quiescent and neutral, then it is immaterial how 
many of such particles are condensed together into a given 
space, for owing to the want of repulsive action in those par- 
ticles, that space will be as much a vacuum to any other gas 
as it ever was. Now it has just been shown that certain 
gases will diffuse into others even though the latter may be 
condensed into a space twenty times less than that which they 
would ordinarily occupy. The vacuum is not the less a 
vacuum because it is contained under smaller dimensions, 
any more than a Torricellian vacuum is less perfect when the 
mercury is made to rise nearly to the top of the barometric 
tube, than it was when there was a vacant space many inches 
in length. Theory would therefore indicate, that tnese dif- 
fusions might take place under all pressures, provided the 
gaseous condition subsists. 

Moreover, the foregoing experiments do not actually furnish 
any proof that gases diffuse themselves into one another with a 
force greater than one atmosphere. It is a mistake to adduce 
them as examples in point, for the fact is that the barrier or 
tissue, far from being passive, exerts a very remarkable action 
in virtue of its absorbing power, a property pre-eminentl}' pos- 
sessed by charcoal, and some other porous bodies. This 
seems to afford an explanation of the whole phaenomenon, 
and furnish an important fact in a physiological point of 
viev/, — that membranes and tissues are occasionally the origin 
and seat of powers of uncommon intensity. 

It will be convenient, for the better understanding of these 
actions, to consider them under two heads. First, where the 
barrier between the media exerts no absorbent action on the 
media ; this will include most of the results of Prof. Graham : 
secondly, where one of the media is absorbed to a much 
greater extent than the other ; this will include all the fore- 
going experiments. 

In the first case, the velocities with which any two gases 



248 Dr. J. W. Draper's Remarks on the 

pass into a vacuum are inversely proportional to the square 
roots of their densities respectively : moreover, the volumes 
that so pass vary directly as the velocities, and therefore may 
be taken as an index and measure of them ; but as the mass 
of each gas is expressed by the product of its density into 
its volume, it may be represented by the velocity multiplied 
into the density; and as the square of the velocity of one 
gas multiplied into its density is equal to the square of the 
velocity of the other multiplied into its density, whatever may 
be the difference of the specific gravity of the two gases, their 
mechanical momentum will always be the same ; the resistance 
they meet with in passing through the tissue is common to 
both, and equal in both cases, and hence the initial velocities 
of diffusion ought to be inversely proportional to the square 
roots of the densities; and as during the progress of the ex- 
periment the impelling force of the one gas is equal to the ex- 
pelling force of the other, the resulting momenta of the two 
currents is still equal, and the final volumes are such as are 
found by direct experiment. 

In the second case. We have first to refer here to a fun- 
damental proposition of dynamics, that when the moving 
force and the matter to be moved vary in the same propor- 
tion, the resulting velocity will be the same. An illustration 
will show the application of this principle to the case in hand : 
if a cylinder of air, fitted appropriately with a piston, com- 
municates with a vacuum by means of a narrow aperture, it 
is immaterial whether the air be allowed to flow into the void 
without any pressure, or whether it be urged by a direct ac- 
tion on the piston ; its velocity as it goes into the void will in 
both cases be the same ; for if it be compressed, the immediate 
action of the force exerted on the piston is to reduce the air 
in the cylinder to such a density that its elasticity shall be 
equivalent to the compressing force; and because the elasticity 
varies as the density, the density of the air will increase with 
the expelling force; the matter to be moved is therefore in- 
creased in the same proportion with the pressure, and the 
final velocity is therefore the same. Now what is here said 
of a cylinder of compressed air, applies evidently to the action 
of barriers, such as sheets of water or India-rubber, which 
are nothing more than perpetual and equable condensing en- 
gines. When one of these is employed, if it increases the 
elastic force of a gas by compressing it, at the same time it 
increases its density, and therefore the velocity of transit is 
the same as though the gas had suffered no action of com- 
pression. 

Such is the case whilst the gases are engaged with each 



Constitution of the Atmosphere. 249 

other in the barrier, but as soon as they are passed from it and 
are beyond the reach of its attractive force, a new condition 
of things takes place; the condensed gas being no longer 
under restraint, expands freely into a void, and when there 
measured, gives a resulting volume totally different to what 
it would have given had not the tissue compressed it. Sup- 
pose, for example, we place on one side of a barrier carbonic 
acid gas, of which it could condense its own volume, and on 
the other atmospheric air on which it exerted no action. 
Whilst the two gases were engaged together in the barrier 
the one would be presented to the other under an elastic 
force double of that which it would have had, if no absorp- 
tion had gone on ; but since its density is directly proportional 
to its elastic force, the continual velocity with which it rushes 
into the other gas is the same as though no compression 
whatever had occurred ; the rate of exchange in the barrier 
is the same as under normal circumstances, that is to say, 
every volume of air replaces 0*8091 of compressed carbonic 
acid; but so soon as this gas has reached the opposite side of 
the barrier and there escapes, its elastic force, being restrained 
by no compression, causes it to assume its original dimen- 
sions. 

This explanation satisfies all the facts, and reduces these 
experiments to the operation of the hypothesis of gaseous 
action ; I would not here be understood to say that there are 
no other disturbing actions going on in barriers except those 
that result from their absorbing power. A great disturbance 
often arises from the circumstance that when two gases are 
absorbed together they experience a greater condensation 
than each would in a separate state. It is therefore impos- 
sible to foretell what the result of diffusing one gas into an- 
other will be, by simply ascertaining how many volumes of 
either alone will be absorbed by the tissue, inasmuch as a 
greater or less condensation may happen when both are em- 
ployed together. 

Variations of temperature, which probably affect the power 
of absorption, and thereby the diffusive volumes, are experi- 
enced by all barriers. When charcoal, or any other porous 
mass, is placed in an atmosphere of gas which it can rapidly 
condense, its temperature rises, the effect apparently depend- 
ing more on the velocity of absorption than on the final 
amount. In the case of ammonia, it does not even require a 
thermometer to discover the increase of temperature, for it is 
very sensible to the touch. On the other hand, when this 
condensed gas makes its escape, a corresponding diminution 
of temperature happens : it is immaterial by what means the 



250 Dr. J. W. Draper's Remarks on the 

liberation of the gas is effected ; the same result uniformly 
follows. If a porous mass, saturated with carbonic acid, be 
exposed to an atmosphere of hydrogen, it absorbs but a small 
quantity of this latter, whilst a very large amount of the 
former is liberated from its condensed state, and the thermo- 
meter indicates a fall of temperature ; the resulting volume of 
the mixed gases being much larger than the original volume 
of hydrogen. And if a porous mass which has absorbed its 
due volume of hydrogen be immersed in an atmosphere of 
ammonia, the resulting volume of the mixed gases is much 
smaller than the original amount, and the porous mass be- 
comes hot. 

The observations here made on the vicissitudes of tempera- 
ture which a porous mass experiences when successively 
immersed in an atmosphere of different kinds, obviously ap- 
ply when the exposures instead of being consecutive are simul- 
taneous. If, for example, a barrier separates carbonic acid 
and hydrogen gas, and absorbs the former to a large amount, 
but exerts little or no action on the latter, then the opposite 
sides of that barrier will be unequally heated. Suppose, for 
illustration, we call that surface of the barrier which looks 
towards the carbonic acid C, and the surface looking toward 
the hydrogen H ; then because of the condensing action of 
the barrier on the acid gas, the surface C will become hot; 
but because this gas as soon as it has passed through the bar- 
rier expands, as into a void, when it reaches the surface H, 
that surface because of the expansion will become cold. We 
see, therefore, that immediately after the action of the barrier 
is first set up, the absorption of carbonic acid takes place 
on a hot surface, and its evolution from a cold one ; whereas 
the absorption of the hydrogen takes place on a cold surface, 
and its evolution from a hot one. A modified result of course 
happens when both gases are absorbed in different degrees, 
and any prediction of the resulting action becomes a matter of 
much difficulty. When the barrier is very thin, or has a high 
conducting power as respects caloric, this distinct surface ac- 
tion may not rigidly occur, but the whole structure experiences 
some rise or diminution, a mean expressive of the condition 
of the two surfaces respectively. 

On the 22nd of November 1837, on analysing atmospheric 
air at this place, there was found in it only 19-60 per cent, of 
oxygen, corroborative results being obtained by the use of 
deutoxide of nitrogen and hydrogen gas ; but the day previous 
and the day following, the proportion was almost 21 per cent. 
This is not an insulated result; I know that on several occa- 
sions during the last four years the proportion of oxygen in the 



Constitution of the Atmosphere. 251 

air has varied in experiments that have been carefully made 
in Virginia. For a length of time these variations were im- 
puted to the use of binoxide of nitrogen, and it was not until 
we made the same observations in using hydrogen gas, that 
the true cause was suspected. I believe that the binoxide of 
nitrogen will always give accurate results, if added to atmo- 
spheric air, in a stream of bubbles, by Hare's sliding rod eu- 
diometer* : one fourth of the deficit is to be taken. 

In the course of these investigations, it has happened to 
me to observe some instances of an action which you have so 
fully described. In a paper inserted in the American Journal 
of Medical Sciences for May 1836, it is remarked, "An im- 
portant circumstance in gaseous analysis may here be no- 
ticed. If a tissue, in the act of transmitting gas or ready to do 
so, be placed in contact with another gas of a different nature, 
disturbance immediately ensues. A cubic inch of nitrogen 
made with phosphorus, but which was found to be contami- 
nated with 4^ per cent, of oxygen, was agitated briskly in a 
phial containing about an ounce of spring-water. In one 
minute the nitrogen gained one per cent, by the agitation. 
The same quantity of nitrogen agitated in a pint of water 
gained no less than eleven per cent, of oxygen. Nor is agita- 
tion or mechanical violence necessary to produce this im- 
portant result. Into a bell filled with water and inverted 
into another vessel, so as not touch it in any point, I placed 
100 measures of a gas, 85 of which were oxygen. After four 
weeks, an analysis was made, and the gas in the bell found 
to contain only 72 per cent, of oxygen, the remainder being 
nitrogen. In this way too, in the lapse of time, from an in- 
verted vessel partially filled with atmospheric air, the oxygen 
will escape into the water, and thence into the atmosphere ; and 
I have twice known this event to take place, so that the resi- 
due did not contain more than three or four per cent, of oxy- 
gen. In many of the most delicate researches of chemistry 
we have this disturbing cause in operation, which has for the 
most part been overlooked. Water is uniformly employed 
in our laboratories as a means of confining gases ; it enters 
largely into our processes of pneumatic manipulation, and 
though we have hitherto neglected its action, it silently dis- 
turbs all our results. An air bell cannot pass to the top of 
a jar without instant contamination; during its residence 
there it is subject to a continued succession of changes ; at no 
two moments is it the same in composition, a perfect freedom 
of communication existing between it and the atmosphere." 

" As an instrument of rigid analysis, the pneumatic appara- 
tus so arranged requires to be used with circumspection. It is 
[* See Phil. Mag. and Annals, N. S., vol. vi. p. 114.] 



252 M. Quetelet's Ohservatio7is on Shooting Stars 



to 



impossible to keep oxygen, nitrogen, or any other gas in its 
original purity, if confined by water. This fluid, which when 
reduced to a thin imperceptible film is instantaneously per- 
meated by almost every substance, undergoes the like action 
in course of time, even in deep masses. Gases are absorbed 
by it, and thrown off by it, in its purest state ; how much more 
complicated then must its action be in that impure condition 
in which it is commonly used ! Connected with this point, 
there is another : if a series of bells stand on a pneumatic 
trough, each will affect all the others, communicating a part 
of its contents and receiving from them in return. A jar con- 
taining binoxide of nitrogen, standing by the side of one con- 
taining common air, seriously affects it. I have noticed that 
two common tumblers, filled with these gases and so placed, 
communicate with each other, and so freely, that in 17 hours 
the tumbler originally filled with atmospheric air contained 
only 9f per ceat. of oxygen. The habit of collecting gases 
at the same trough that is destined to preserve others is very 
exceptionable : we place the disturbing agency in circum- 
stances the most favourable for its action. All operations of 
washing are liable to the same strictures." 

I fear I have intruded upon you too long a letter. I have 
been encouraged to do so ; for we are accustomed in America 
to associate with your name whatever there is of exactitude 
in chemistry. In gaseous mechanics the most important ob- 
servations are due to your labours ; and anything that may 
have even a remote bearing on the subject, will, I am per- 
suaded, meet with acceptance from you. 

Your obedient servant, 

John W. Draper. 

XXXIV. Observations on Shooting Stars on the Nights of the 
9th, 10th, and 1 Ith of August 1838. By M. Quetelet, 
Director of the Observatory of Brussels, S^c. S^c. t$-c., and by 
E. J. Cooper, Esq. M.P.* 

To Richard Taylor, Esq. Editor of the Philosophical 
Magazine. 

Dear Sir, 
T RECEIVED the letter of which the following is an ex- 
■*- tract the day after the last meeting of the Physical Section 
of the British Association at Newcastle, and was therefore 
not able to comply with the request of M. Quetelet to pre- 
sent the interesting particulars which it contains to the notice 
of the Section. It seems to me that it I shall equally well effect 

* See Lond. and Edinb. Phil. Mag., vol. xi. p. 261. 



on the niglits of the 9th, 10th, and 1 Ith of August. 253 

M. Quetelet's objects by calling attention to his observations 
in your Journal, and by requesting that if any similar ones 
have been made in Great Britain, they may be communicated 
to you. Very respectfully yours, 

London, Aug. 30, 1838. A. D. Bache, 

President of the Gir. Coll. 
Philadelphia. 

Extract of a Letter from M. Quetelet, Director of the Obser- 
vatory of Brussels, to Prof, A. D. Bache, of Philadelphia. 

" I observed the number of shooting stars visible here (at 
Brussels) on the nights of the 9th, 10th, and 11th of August. 
On the first of these nights the sky was almost entirely co- 
vered with clouds, and I saw but two shooting stars. 

" On the night of the 1 1th, until nearly midnight, about one 
third of the sky towards the zenith was generally clear. 
Subsequently it was only clear at intervals, and towards two 
o'clock it rained. I was assisted in my observations by t\^ 
other persons ; and notwithstanding the unfavourable circum- 
stances of the night we saw many shooting stars, besides se- 
veral very brilliant meteors, with nearly all of them a luminous 
train. The uniform direction of their motion was further re- 
markable. Below is the result of our observations on the 
night of the 10th, giving the directions of the paths of the 
shooting stars and the hours between which the numbers 
given were seen. 
49 directed from between the north and east towards the 
opposite quarter of the sky. 

1 between the south and west towards the opposite quar- 
ter of the sky. 

4 between the south and east towards the opposite quar- 

ter of the sky. 
1 1 between the north and west towards the opposite quar- 
ter of the sky. 

5 from east to west. 
1 from west to east. 

4 from north to south. 
1 from south to north. 

76 

1 1 not well determined. 

87 total number seen. 
Of these were seen : 

16 between 9 — 10 o'clock. The observations about 9 
o'clock were interrupted for aboutl5 minutes by clouds. 



254 Mr. K J. Cooper's Observatio7is oji Shooting Siars 

29 between 10—11 o'clock. 

39 between 11, and 11 and SO minutes. The sky then 
clouded over. 
3 after midnight in the clear intervals. 
" I estimate at double the number just given what we should 
probably have seen had the weather been favourable. 

"On the night of the 11th the sky was clear until towards 
two o'clock. At half past two it was covered with clouds. 
I had on this occasion three assistants. We saw 
2 shooting stars before 9 o'clock. 
34 between 9 — 10 o'clock. 
19 between 10 — 11 
24 between 11 — 12 
32 between 12 — I 

12 between 1 — 2 
10 between 2 — 3 

2 after 3 o'clock. 

135 total number of shooting stars which were seen. 

The directions of the motions were 
71 from between the north and east towards the opposite 
part of the sky. 

3 between the south and west towards the opposite part 

of the sky. 
16 between the south and east towards the opposite part 

of the sky. 
10 between the north and west towards the opposite part 

of the sky. 
10 from east to west. 
2 from west to east. 

13 from north to south. 
6 from south to north. 



131, leaving four, the directions of which were not well de- 
termined. 
"The shooting stars of the 11th, though fine, were less so 
than those of the 10th. The general direction, as has been 
seen, was from the north-east towards the south-west." 

[The following notice on the same subject has been commu- 
nicated by the Rev. T. R. Robinson, D.D. of Armagh.] 

Extract of a Letter Jrom Edward J. Cooper, Esq., M.P. 

" My dear Dr. Robinson, Geneva, Aug. 16, 1838. 

*' I have not been able to do much in arranging the observa- 
tions made of falling stars on the nights 10 — 11 instant, as 
I only received those made by my companions last night. 



on the nights of the 9thf 10//?, and llth of August. 255 

The total number seen from 8^ to 16'' was upwards of 380. 
The number actually observed = 373, of which 123 fell to my 
list. My companions were M. Wartman and his two sons, 
M. Miiller of the Observatory, and M. Borel, a friend of his. 
At 8*" two banks of clouds converged to a point on the horizon 
N. 40 E. This point moved subsequently about 5° more to 
the E. ; and at 9'' 45" the clouds had become much darker, 
and the angle of convergence had greatly increased. At lO'' 
they had become white and thin, and nearly concealed the 
north from the horizon to a Lyrae. About 14'' they had moved 
northward, and the point of convergence was at N. 35 E. 
Heavy dew, night perfectly calm. Three of the stars passed 
apparently over clouds. I can now merely class my own ob- 
servations as follows. I find I am too late for post today, so 
will endeavour to class the total. Aug. Kith. I have found 
that it requires a very long time, so I can only give you the 
total numbers from and to each constellation. 1 shall place 
the numbery^OOT before, and the number to after, the name of 
the constellation. I have not time to check my work. 

1 Hon. Fred. 3. 
"Lizard" 1. 

2 Librae 5. 
Lyncis 4. 

17 Lyrae 12. 

Mont. Menal. 1. 



6. 



1. 



16 Andromed. 

1 Antinoi 14. 

Appar. Sculpt. 

10 Aquarii 6. 
16 Aquilae 13. 

2 Arietis 2. 

11 Aurigae 7. 
18 Bootis 28. 

6 Camelop. 2. 
5. 
10. 

20 Cassiopeiae 11. 
128 Cephei 10. 

1 " Cercle Murale" 1 

1 " Cervus Arcticus" 
Ceti 7. 

Custod. Messium 
Comae Ber. 1„ 
Coronas Bor. 14. 
Cygni 17. 
Delphini 0. 
Draconis 21. 

Equus Min. 1. 

2 Gemini 6. 

21 Herculis 18. 



2 Can. Ven. 
5 Capricorn. 



5 
1 


13 
26 

7 
40 





1 Ophiuchi 9. 

2 Orionis 4. 

16 Pegasi 15. 

17 Persei 13. 
Pise. Aust. 1. 

3 Piscis 2. 
Ram. et Cerb. 

4 Sagittae 2. 
0. 1 Sagittarii 6. 

10 Serpentis 18. 

2 Scut. Sobiesk. 

2 Scorpionis 8. 

6 Tauri 6. 

2 Taur. Poniat. 

Telescopii 1. 

2 Trianguli 5. 
31 Urs. Maj. 29. 
22 Urs. Min. 21. 



0. 



6. 



Virginis 1. 
"You will perceive that the numbers here particularizal do 



256 Dr. Schoenbein's Conjectures on the 

not accord with the grand total, nor can I, as I have already 
said, check them. I think however that there is enough to 
prove that on the 10th of August at least there has been 
nothing to support the idea of a common focus. I also must 
add, that on the following night there were only 3 per hour 
less in number." 



XXXV. Conjectures on the Cause of the peculiar Condition 
of Iron. By Dr. Sch(enbein.* 

CEVERAL attempts have already been made to explain 
^ the pecuhar condition of iron. Dr. Faraday's hypothesis 
upon that subject is certainly the most ingenious and most 
plausible of all the theories as yet brought forward, but 
there are some facts pointed out by me elsewhere, which do 
not well agree with the views of that distinguished philosopher. 
As the matter alluded to is of some importance with respect 
to electrical science, and all the theories hitherto announced 
upon the cause of the anomalous relations of the iron having 
failed, I may, perhaps, be allowed to suggest some ideas re- 
garding the delicate point in question. But before doing it 
I must not omit to say, that I do not lay much stress upon 
my conjectures, and that I have only ventured to make them 
public, because I hope they will engage some philosopher 
more able than myself to take up the subject, and clear up by 
new investigations the darkness which still invests the cause 
of the inactivity of iron. 

Chemistry in our days accounts for the difference of qua- 
lities exhibited by what are called " isomeric bodies" by 
asserting that the same number of particles of the same ele- 
ments are capable of grouping themselves in different ways. 
Now if heterogeneous atoms be capable of combining in va- 
rious manners, is it not possible that homogeneous ones may 
do the same, and in such a way as to give rise to substances 
essentially distinct from each other not only with regard to 
their physical, but also as to their chemical properties ? Sul- 
phur, selenium, phosphorus, and carbon prove indeed that 
simple substances are capable of assuming states almost as 
different from each other as any two isomeric bodies are in 
qualities. It is true, the difference of properties which we 
sometimes observe in the same element is generally referable 
lo a modification of the cohesive attraction of its molecules 
brought about by the agency of heat; but I am almost sure, 

• Communicated by Mr. Faraday, to whom it had been addressed by 
the Author. 



Cause of the peculiar Condition of Iron. 257 

that the chemical relations of a body are, more or less, modi- 
fied also as often as a change of its cohesive state is effected. 
Sulphur for instance, in its peculiar (viscid) condition, phos- 
phorus being liquid at the common temperature, selenium 
in its half fluid state, carbon as diamond, all these simple 
bodies are, most likely, in a chemical point of view, different 
from what they are in their usual condition. We certainly 
want as yet tests to ascertain the chemical difference which 
exists, for instance, between viscid and common sulphur, &c. ; 
but though this be the case, analogy, I think, makes up for 
that want, and allows of our making an assertion of the 
kind. There are, indeed, many instances in chemistry which 
show a most intimate connexion existing between the cohe- 
sive state of a body and its chemical relations, and it would 
be quite superfluous to cite any such example. 

Now, if by means of heat, and in some rare cases by that 
of light too, a number of simple substances can undergo an 
essential change as to their molecular aggregation, why should 
an agency so powerful as current-electricity, which parts 
asunder elements most intimately combined with one another; 
— I ask, why should such a force be incapable of modifying the 
natural cohesive state of bodies, for instance, that of iron ? 
The conjecture, that the current which passes from that metal 
into a solution of blue vitriol modifies the molecular consti- 
tution of iron so as to destroy the affinity of the latter for the 
oxygen contained in the oxide of copper and disengaged from 
water by electrolytic action, is indeed a new and rather a bold 
one, but I should think no more so than many other conjec- 
tural views, which are now much in vogue with chemists and 
considered as very plausible. The fact that iron once being 
rendered inactive does not remain in its peculiar condition, is 
no proof against the correctness of my idea ; for it may be 
said, that the modification of the molecular constitution caused 
by the current is, as it were, a condition forced upon the metal, 
a strained state, which ceases to exist as soon as its cause 
ceases to act. The condition may properly be compared to 
that in which the particles of a bent steel-spring exist. 

The circumstance that inactive iron can remain untouched 
for any length of time within nitric acid of a certain strength 
without the agency of a current, is a fact which may appear 
to be quite irreconcilable with my hypothesis. I do not think, 
however, that such is the case. In the first place we must 
suppose that something like a " vis inertia " comes into pla}'-, 
that is to say, to a certain degree a tendency of the iron par- 
ticles to remain in their newly assumed juxtaposition ; but on 
the other hand we must also admit the existence of some ac- 

Phil.Mag. S,3. Vol. 13. No. 82. Oct, 1838, S 



258 Dr. Schoenbein's Conjectures on the 

tion on the part of the acid upon the inactive iron. It is a 
well-known fact that fused phosphorus does not become solid 
at the common temperature if surrounded by a strong solu- 
tion of potash* ; and according to the experiments which I have 
made on the subject, phosphorus being in the circumstances 
mentioned can be cooled down nearly to the freezing point 
without becoming solid, whereas when covered with water it 
becomes solid at 104° Fahr. Now if the presence of a solution 
of potash prevent phosphorus from assuming its solid state, 
nitric acid by an analogous action may force the particles of 
inactive iron to remain in their peculiar relative position. 

Having ventured myself so far into the regions of conjec- 
ture, I may, perhaps, be allowed to continue my course a little 
longer in that direction. For aught I know, all chemical phi- 
losophers tacitly acknowledge that the chemical attractive 
force which a particle of any element exerts with reference 
to a particle of any other simple body is equal on every one 
of its sides, provided the distance between the two particles 
remains the same. Now the peculiar state of iron leads 
me to suspect, that the particles of that metal have each ol 
them two chemical poles, at least with regard to oxygen, one 
pole which attracts the latter body, and another pole which 
either exerts no attraction for oxygen or which repels it. 
Supposing each molecule of iron to be possessed of such 
polar sides, it may be conceived, that a current which passes 
from the metal into an oxi-electrolytic fluid, into a solution of 
blue vitriol for instance, directs these particles so as to place 
their attractive poles (attractive with regard to oxygen) to- 
wards the axis of the current, or inwards with respect to the 
surface of the metal, and the repulsive ones towards the elec- 
trolytic fluid. Such a position of the particles would prevent 
them from acting either upon the oxygen disengaged at them 
by electrolytic action or upon the oxygen contained in the 
oxide of copper. It is a matter of course, according to my 
hypothesis, that the arrangement of the poles of the mole- 
cules of the iron would be the reverse of that just spoken of, 
in case the metal acted the part of the cathode of a current. 
I have shown that a piece of iron rendered inactive by its 
having been made the positive electrode within common nitric 
acid, is turned active again by being made the negative one. 
I must, however, not omit to state, that in order to make the 
hypothesis agree with all the facts known respecting the pe- 
culiar condition of iron, we are obliged to suppose that the 
polarity of the iron particles exists only with regard to oxy- 

* The presence of the solution of potash, however, is not required to 
retain the phosphorus in the liquid state. See Phil. Mag. and Annals, 
N.S., vol. jii. [>, 144.— -Edit. 



Came of the peculiar Condition of Iron. 259 

gen which is either in a combined state or set free by electro- 
jylic action, and by no means to oxygen which is in its usual 
condition. If iron be voltaically associated with platina and 
put into water containing oxygen dissolved, the former metal 
is oxidized whether the platina be plunged into the fluid 
before or after the iron. If zinc be the substance put into 
voltaic association with iron, the latter is not in the least af- 
fected by the oxygen, which the water holds dissolved. For 
these last four months I have kept a combination of both 
metals within common water, which has been continually ex- 
posed to the air, and the surface of the iron is at this present 
moment as brilliant as it was when I put that metal into the 
water ; whilst the zinc appears surrounded by a thick cloud 
of its oxide. In the two cases stated the electro-chemical 
laws hold good, whereas they do not at all agree with the 
phaenomena which are referable to the peculiar condition of 
iron. I must openly confess that the different way in which 
the same current makes the iron act upon the oxygen appears 
to me as rather unfavourable to my hypothesis of a chemical 
polarity of the iron particles ; but on the other hand it must 
be allowed, that the fact alluded to is likewise very much at 
variance with the principles of the electro-chemical system 
of the present day. 

There is another objection to which my hypothesis will, per- 
haps, be thought liable. It may be said that the solid state 
of iron does not allow its particles the motion required for 
obtaining the peculiar arrangement of their poles mentioned. 
It is a point generally adopted by philosophers, that the 
atoms of no body do immediately touch each other, and it is 
supposed that the distance at which any two contiguous par- 
ticles are placed from each other surpasses by far the diame- 
ter of each atom. If such be the case, I cannot conceive 
why the molecules of iron should not be capable of being 
turned by some force, being superior to that by which they 
are kept together under ordinary circumstances. There are, 
indeed, some facts which put it beyond doubt that the molecu- 
lar constitution of a solid body may be essentially modified 
without having recourse to its liquefaction or vaporization. 
Gustave Rose, in a very interesting paper lately published in 
PoggendoriF's Annalen*, has demonstrated, that arragonite 
can easily be transformed into calcareous spar by moderately 
heating the former substance. Such a change cannot take 
place without an internal motion of the particles of carbonate 
of lime, the form of crystallization as well as the specific gra- 
vity of the compound becoming considerably modified under 

• And of which a translation appeared in Lond. and Edinb. Phil, Mag., 
vol. xii, p. 465.— Ecu. 

S2 



260 Dr. Schoenbein 07i the peculiar Condition of Iron. 

the circumstances. Now what heat is capable of effecting in 
one case, a current, I think, must be able to do in another. 

As to the arrangement of the molecules of common iron 
with regard to the relative position of their chemical poles, it 
must be supposed to be similar to that of Ampere's molecular 
currents in the same metal before its being magnetized, that 
is to say, quite irregular. From such being the case it would 
follow that the surface of a piece of common iron is formed 
of attractive and repulsive poles, or what comes to the same 
thing, that the metal without being placed under the influence 
of a current of a certain direction, is to be chemically affected 
by oxygen which is in the peculiar state before mentioned. 

It is not impossible that the supposed chemical polarity of 
the molecules of iron is in some way or other connected with 
the eminently magnetic properties of that metal, and it may 
even be imagined, that the current which is suspected of circu- 
lating round each iron particle has its source in the said po- 
larity. As far as I know. Ampere has only postulated the 
currents in the iron, or rather inferred them from a certain 
number of facts, and given out no opinion whatever as to 
their ultimate cause. The passage of a current through iron 
must at any rate have some influence upon the relative posi- 
tion and motion of the supposed molecular currents of that 
metal, and changing the direction of these currents may also 
determine a modification of the chemical relations of iron. 
Pursuant to my hypothesis nickel and cobalt ought to be 
quite similar with regard to the phjenomena of inactivity. 
Such, however, as formerly shown by me, is not the case ; but 
on the other hand I must say, that my experiments were 
made upon such a small scale and were so few in number, 
that I do not yet dare to draw any conclusive inference from 
them. 

Isomerism and dimorphism, generally speaking so closely 
connected with one another, are phasnomena which have, 
perhaps, also something to do with chemical polarity. Up to 
this present moment they remain unaccounted for; but if we 
suppose that the particle of one substance exerts towards the 
particle of another different degrees of attraction, according 
to different relative positions of these molecules, we can con- 
ceive the possibility of two bodies forming a variety of distinct 
compounds, though the ratio in which their constituent parts 
enter into combination should remain the same. 

Agreeably to such hypothesis a series of isomeric bodies 
would be nothing but [bodies constituted by the operation 
of] different sorts of chemical equilibrium between the same 
constituent parts. It would also follow from the hypothesis, 



Prof. Apjohn on the Specific Heats of the Gases. 261 

that amongst such a series of isomeric bodies, there is one 
in wliich the chemical equihbrium is stable, that is to say, the 
relative position of the chemical poles of the heterogeneous 
atoms such as to allow the greatest attraction between the 
component parts. 

In closing this paper I cannot but repeat what I said at the 
beginning of it, namely, that I do not attach much import- 
ance to the views just now developed, they being entirely hy- 
pothetical; nevertheless I think them not altogether unworthy 
of being taken into consideration. If they should happen to 
excite happier ideas upon the subject treated of in my paper, 
they will not have been quite useless. 
Bale, May 24, 1838. 

XXXVI. The Specific Heats of the Gases as deduced hy Dr. 
Apjohn, compared isoith the more recent Jlesidts o/' Dr. 
Suerman. By James Apjohn, M.D., M.R.I.A., Professor 
of Chemistry in the JRoyal College ofSurgeons, Ireland. 

To the Editors of the Philosophical Magazine and Journal, 
Gentlemen, 

T is known to some of my scientific friends that I have 
been for a considerable time engaged in experiments for 
determining the specific heats of the more remarkable gaseous 
bodies ; and indeed several of the results at which I have ar- 
rived have been communicated to the public through the re- 
ports of the British Association and the pages of the Philo- 
sophical Magazine.* The entire of my researches on this sub- 
ject have some time since been laid before the Royal Irish 
Academ}', and have appeared in a connected form in the vo- 
lume of its Transactions which has just issued from the press. 
As, however, the circulation of the Transactions is necessarily 
limited, and, also, in order that I may set myself right with the 
public upon some points in reference to which I have been 
misapprehended, I am anxious to avail myself of the pages of 
your Journal, to draw attention to the efforts which I have 
made towards the solution of a problem of acknowledged diffi- 
culty and great importance. I have also another object in ma- 
king this hasty communication, viz. to bring under the notice 
of British philosophers the recent very able and valuable in- 
vestigations of Suerman, a copy of whose memoir on the spe- 
cific heats of gases has recently come into my possession. 

Dr. Suerman has, as will be seen, adopted my method, and, 
by means of a very elaborate apparatus, has arrived at con- 
clusions which, as I shall show, correspond very closely with 

[* See L. and E. Phil. Mag., vol. vii. p. 385.] 



I 



262 Prof. Apjohn on the Specific Heats of the GaseSf 

mine. Let me not, however, be misunderstood. Dr. Suer- 
man has borrowed nothing from me, for before he had seen 
my first paper on specific heats he had resolved upon em- 
ploying the method in question in the same research*. So 
far from having reclamations to make, I feel myself his debtor. 
He has frankly admitted my priority, and spoken of my ex- 
periments in terms I fear much too flattering. 

Before proceeding to my immediate object it will be neces- 
sary to remind the reader that in November ISSif? I commu- 
nicated the following formula for the solution of the dew-point 
problem to the Royal Irish Academy : 

/-// = /^ _ A X -^ 
■^ -^ 88 30 ' 

in which y" is the force of vapour at the dew-point, f the 
same at the temperature of the wet thermometer, d = f — t' 
the difference between the indications of the wet and dry in- 
struments, p the existing, and 30 the mean pressure. 

In investigating this expression it was assumed that the spe- 
cific heat of air and the caloric of elasticity of aqueous vapour 
are constant, at least within the limits of the variations, in these 
latitudes, of atmospherical temperature and pressure, an hy- 
pothesis the strict accuracy of which cannot be admitted. 
Preparatory therefore to the application of the formula to the 
investigation of the specific heats of gases, it became necessary 
to give it its most comprehensive form, substituting for the 

numeral coefficient — — the factors of which it is composed, 

88 

and introducing the consideration of density, in order that 
the expression may be true generally of the various elastic 
fluids. The steps which have conducted to such general ex- 
pression I shall here give, partly because I have not published 
them elsewhere, and partly because my investigation of the 

d 7) 

formulay" r=i f — — — - x ~~ has been by some considered 

as complicated and obscure. When, in the case of the wet 
thermometer, the stationary temperature is attained, the ca- 
loric which vaporizes the water is necessarily exactly equal to 
that which the surrounding gas imparts in descending from 
its proper temperature to that of the moistened bulb. From 

» " Tandem opus aggressus, et occupatus in idoneo parando supellectili, 
diarium accepi Anglicum, quo in collegio, quod Dublini habetur, Chemiae 
professoris Apjohn continei)atur disquisitio, ex eodem illo principio 
fluidorum elasticorum calorem specificum derivans. Primum, quid sileam? 
Animo despondebam, quum novitatis colorem, quae mihi praecipue arride- 
bat, de nieo evanescere viderem proposito." (Preface, p. viii.) 

[t See Lend, and Edinb. Phil. Mag. vol. vi. p. 182.] 



as deduced by himself and Dr. Suerman. 263 

this consideration, and the additional hypothesis that the gas 
so cooled by successive contacts with the moistened bulb is sa- 
turated with humidity, we can deduce the following equation : 

in which f" ovf have the significations already assigned to 
them, while m! and m represent, the former the amount of va- 
pour which would be formed by the caloric evolved from a given 
bulk of the gas in cooling through t — t' degrees, the latter the 
maximum quantity which the same volume of such gas could 
contain at the temperature t'. The correctness of this de- 
duction is easily shown. For m being the total quantity of 
moisture in the gas, and m' the quantity introduced into it, 
7» — m'will be the quantity it already contained ; so that, since, 
when the temperature and volume of vapour are both given, 
its elastic force is proportional to its quantity, we shall have 

m : m—iri : :/"' -.f" 
a proportion which gives, as above. 

In arriving at this conclusion, we have assumed that the air 
which is cooled by contact with the moistened bulb becomes 
saturated with humidity. This is the only premiss which we 
have employed about which a question can be raised. That it 
is brought, however, into such condition, no one can, I con- 
ceive, entertain a doubt who reflects upon the very low con- 
ducting power of air, and the consequent impossibility of its 
communicating caloric to the moistened bulb unless by actual 
contact, a condition which can scarcely be fulfilled without 
the entire of the cooled air being at the same time carried to 
the maximum degree of humidity. 

In the expression ioxf" given above, y may be considered 
as known, the corresponding temperature t' being the result 
of an observation. In order, therefore, to render the formula 
available it will only be necessary to determine in known terms 
values of w' and w, which may be done in the following man- 
ner: 

Let a be the specific heat of the gas under a constant press- 
ure, and e the caloric of elasticity of aqueous vapour at t\ 
the stationary temperature of the wet thermometer. It is evi- 
dent that a grain of the gas in cooling through t — t' — d de- 
grees gives out the caloric necessary for raising the tempera- 
ture of a grains of water through the same number of degrees. 
But the caloric which heats a grains of water d degrees would 



264< Prof. Apjohn on the Specific Heats of the Gases, 
convert into vapour having the temperature t' an amount of 

7 

the same fluid represented by grains. Hence one grain 

of the gas in cooling through d degrees evolves heat adequate 
to the evaporation of grains of water at the temperature 

shown by the wet thermometer ; or, if we divide by — , — 

■^ e a 

grains of the gas in cooling through d degrees extricates heat 
which will vaporize d grains of moisture at /'. For m' there- 
fore in the formula f 

d may be substituted. 

Now, supposing the gas to be atmospheric air, and that 
100 cubic inches of this weigh 31 grs., the volume in cubic 

e 
inches of — grains of it at 60° and under a pressure of 30 

will obviously be 

_e_ 100 
a ^ 31 
and at any other temperature t\ and pressure j), 

e 100 44<8 + ^' 30 

« ^ "sT ^ ~508~ ^ y 

an expression which, as the volumes are reciprocally as the 
densities, will, for any gas whose specific gravity is 5, become 

e 100 448 + 1' 30 
as ^ S\ ^ SOS ^ 'p'' 

Let this be multiplied by ,,^,j x 4;7 x '625 x 31, the 

448 + ^ 30 

weight of a cubic inch of aqueous vapour of maximum tension 
at temperature t\ and the product, viz. 

e 100 448 + ^' 30 508 /' 

— X -rt- X — -„Q^ X X ■ ■- , ^, X •(— X'625X'31 = 

as 31 508 p 448 + r 30 

e f 

X ^^ X -625, 

as p 

will be the maximum amount of moisture which can be con- 

, e 
tained in — grains of the gas at temperature t', and pressure 

p, and is therefore the value of m. 



as deduced hy himself and Dr. Suerman. 265 

If therefore we revert to the equation 

and substitute in it for m' and m their values, namely <f, and 

e f 

— X - — X '625, we are conducted to the following final 
as 30 ^ 

equation, which includes the solution of the dew-point pro- 
blem, 

sad V _/',_48s«^ ^_ 

In the case of atmospheric air 5 = 1 ; so that for the pur- 
poses of the meteorologist 

/"=/'- i^x^, (B.) 



e 



which, if we assume a — '267, and e = 967° + 212° —50° 
= 1129, becomes 

/-// _ /-f _ A X A 
•^ -^ 88 30 ' 

the expression which I have used in my paper on the dew- 
point. Now though a and e are not, as is assumed in this 
latter expression, constant, the mean values which are assigned 
to them are sufficiently exact for all practical purposes. This 
I believe I may say I have established by three distinct series 
of experiments, for the particulars of which, however, I must 
refer to my second paper on the dew-point. 

Before proceeding to other topics, I wish to state that an 
expression identical with (B) was obtained some years ago by 
Mr. Ivory. His method, however, was so totally different from 
mine, that those who examine both will, I make little doubt, 
consider it scarcely necessary for me to disclaim, as I have 
elsewhere done, any knowledge of his investigations at the 
time I gave publicity to my own results. In perusing also 
Dr. Suerman's thesis already referred to, I find ascribed 
to Gay-Lussac a formula for dry air which scarcely differs, as 
shall be hereafter shown, from one which may be deduced 
from mine. Again, in the first part of Professor Graham's 
Elements of Chemistry recently published, and which he was 
good enough to send me, I find, in a note to page 82, a 
formula ascribed to Dr. August which is in form the same 
with that which I have given, but adapted to Reaumur's 
thermometer. The coefficient, however, of d is too great by 
about one fourth ; for the formula in question (adopting in it 
the notation already employed,) is 



266 Prof. Apjohn on the Specific Heats of the Gases, 

/" = /' - '^^^^P 

whereas, assigning to a its ordinary value '267, my expres- 
sion, when brought to this shape, would be 

Now, the only way of accounting for this difference is by 
supposing Dr. August to consider the value of a, the specific 
heat of air, to be not '267 but 'S^9, an assumption which it is 
scarcely necessary to say is altogether inconsistent with ex- 
periment. Professor Graham observes of this formula, " It 
was employed by Humboldt and G. Rose in their recent ex- 
pedition to Siberia, and (as I was assured by the latter) with 
excellent effect." This testimony would have startled me 
much had it been stated that contemporaneous observations 
were uniformly made with a condensation hygrometer. But 
as this is not asserted, I feel the less reluctance in declaring 
that the formula in question, however satisfactory it may seem 
to the eminent philosophers just named, is undoubtedly er- 
roneous. In an observation of theirs quoted by Professor 
Graham, t being 74<°-9, t' 56°-9, and p 30-17, by the method 
of August, f" is inferred to be •22678, whereas by mine it 
would be "26596. Adopting the former value the dew-point 
f would be 35°'6, while, if the latter be correct, it is 40°*1. 
Now from the many and severe tests to which I have put my 
own method, I do not hesitate to assert that the first-mentioned 
determination of the point of deposition makes it at least four 
degrees Fahrenheit too low. 

But to return from this digression to the subject of specific 

heats. From equation (A) or/" =/' ^ so ^^ 

readily deduce the following expression for the specific heat 
of a gas, viz. 

{f'-f)"e 30 
48 5 c/ p 

which, when the gas is perfectly dry, or, in other words, 
wherey" = becomes 

f'e SO 

4t8s a p 

This is the specific heat of the gas under a given weight. 
Hence as the specific heats of equal volumes of different gases 
are equal to the specific heats of equal weights multiplied by the 



as deduced hy himself and Dr. Suerman. 267 

specific gravities, the general expression for the specific heats 
of equal volumes will be 

^ X ^ (C.) 

Now, in this expression d = t—1),f' the force of vapour 
at t\ and^ the existing pressure, are given by observation; 
e is also a known quantity, being, according to the most ac- 
curate experiments, and upon the hypothesis that the sum of 
the sensible and latent heat of aqueous vapour at all tempera- 
tures is a constant quantity, equal to 1 179 — ^. By aid, there- 
fore, of a hygrometric observation with a wet and dry ther- 
mometer in any gas, the barometer being also observed, the 
specific heat of a given volume of such gas may be calculated. 
Such is the method which, as far as my knowledge extends, 
I have been the first to propose and practise. To this general 
explanation it is only necessary to add that, at the close of 
each experiment the gas operated with was subjected to ana- 
lysis, and a correction made for the per centage of atmo- 
spheric air which it was found to include, by means of a for- 
mula which may be thus investigated. 

Let a be the calculated specific heat of the mixture of air 
and gas, a' the true specific heat of the gas, n the number of 
volumes of air in 100 of the gas, and c the specific heat of air 
as deduced by means of formula (c) from a distinct experi- 
ment with air alone. Then, on the principle that the specific 
heat of the mixture of air and gas multiplied by its volume is 
equal to the sum of the products of the respective volumes of 
air and gas multiplied by their respective specific heats, 

a' (100 — w) + we = 100 « 

which gives 

, {a—e\n 

a = a + — . 

^ 100— n 

As examples of the course to be pursued, I shall adduce 
the following observations made successively on air and hy- 
drogen, on the Sth of August 1835. 

t "^ t' d p 

Hydrogen 68 4-8 20 30*1 U 

Air 68 .43 25 SO'll* 

By applying to these results the equation a = -^-^ x — 

we get 

Specific heat of air = '2767 = c 

Specific heat of hydrogen = '4090 = a. 

But the hydrogen upon analysis was found to contain 5 per 



268 Prof. Apjohn on the Specific Heats of the Gases, 
cent, of air. Hence, the specific heat of the hydrogen sup- 
posed pure, as deduced from the equation a' = a-{- > , 

becomes -4151. And as -2767 : '2670 : : 4151 : '4005, the 
specific heat of hydrogen compared to that of an equal volume 
of air under a pressure of 30 when water is represented by 
unity, or, what amounts to the same, when air is '267. 

In order to the determination of t and /' the wet and dry 
thermometers were introduced into a glass tube through which 
the gas, first dried by bubbling through oil of vitriol, was 
made to pass in a rapid current, by means of pressure with 
a board upon a large bladder in which it was contained; and, 
as soon as the wet thermometer, which by exposure to the 
dry air or gas rapidly falls, acquired a stationary temperature, 
its indication and that of the dry instrument were registered. 
In the case of air there was no difficulty in reaching this sta- 
tionary point, it being obviously only necessary to maintain 
the blast sufficiently long. It would, however, have been in- 
convenient to employ a sufficient quantity of the other gases 
to ensure the production in each case of a maximum degree 
of depression ; so that, when for any of these t and t' had to be 
observed, the wet thermometer was first brought nearly to its 
stationary point by a current of atmospherical air. The de- 
pression proper to the gas was now easily obtained by causing 
the blast of air to be immediatelij succeeded by one of the gas, 
and which in consequence of this contrivance it was, generally 
speaking, found necessary to maintain only for a few seconds. 
For a more detailed description, and a wood-cut of the ap- 
paratus, I must refer to the report published by the British 
Association of its proceedings in Bristol. The results ob- 
tained by the method just explained are presented in the 
following tables. Table (1.) relates to atmospheric air alone; 
table (2.) to the other gases. In table (3.) we have the mean 
results given in table (2.) referred to atmospheric air repre- 
sented both by "267 and by unity. The numbers in the last 
column of table (3.) are the specific heats of equal weights, 
and are got by dividing the numbers in the preceding column 
by the specific gravities of the gases to which they respectively 
belong. 



as deduced hy Jiimselfand Dr. Suerman. 
(1.) 



269 





t 


t' 


d 


;' 


a 


June 21. 


58-8 


38^4 


20-4 


30^014 


•2912 


27. 


52-7 


34-9 


17-8 


30-225 


•2935 


July 31. 


64^5 


41-2 


23-3 


30-330 


•2773 


Aug. 1. 


67-3 


42 


25-3 


30-140 


•2624 


4. 


68 


43 


25 


30-114 


•2161 


5. 


67 


42-4 


24^6 


30-000 


•2768 


7. 


66 


44-7 


24-3 


30-218 


•2657 
■2116 



(2.) 



. , \ June 27, 

A^°'^ } July 31. 



Carbonic 
Acid... 

Carbonic 
Oxide. 



Hydrogen 



Nitrous 
Oxide 




53-8 35-5 
65 41-3 



60 

53-8 

65^2 

67-3 
67-5 
66-2 

59 

52-; 
65 
68 

67-5 
65 



40 

36-5 

42-7 

43-5 

43 

42-4 

42-8 
38-9 
46 
48 

44-5 
42-5 



18-3 

23-7 

20 

17-3 

22-5 

23-8 
24-5 
23-8 

16-2 
13-4 
19 
20 



30-225' -2915 
30-330j -2735 

30^0 14' -3135 
30-225, -3178 
30-330, -3021 

30-140, -2952 
30-000, -2874 
30-218 -2774 



Air per 
cent. 



30-014 

30-225 
30-330 
30-114 



23 30-114 
22-5 30-218 



•4262 
•4475 
•4000 
•4092 

•3173 
•3013 



11-4 
12 

8-2 



4 
7 

7-5 
5 



■2915 
•2735 

•3137 
-3211 
•3043 

■2952 

•2874 
•2774 

•4317 
•4590 
•4099 



Means. 



•S}-^^~ 



4151 -4005 



27-5 -3327 
14 -3071 



-2876 
•2921 
•2933 

•3003 

-2772 
-2825 

•3961 
•4175 
•3946 



•3210 
•3085 



•2910 



•2863 



•4022 



•3147 





(3.) 








Specific Heats of equal 
Volumes. 


Specific Heats 
of equal 

Weights. 




•2670 
•2660 
•2710 
•4022 
•2910 
•2863 
•3147 


rooo 

•996 
1-015 
1-506 
1-090 
1-072 
1179 


1-000 

1-024 
-920 

21-826 

•715 

1-102 

•773 




Oxygen, (by calculation) 

Hydrogen 


Carbonic Acid 


Carbonic Oxide 


Nitrous Oxide 





Upon these results I never placed much reliance. The 
apparatus employed was very imperfect, particularly in not 
allowing more than a single experiment with the same quan- 
tity of gas; and I also saw reason to doubt that I had in every 
instance by means of it accomplished perfect desiccation. 
The difference, however, between my number for hydrogen 
and that of De la Roche and Berard, which has hitherto 



270 Prof. Apjohn o« the Specific Heats of the GaseSf 

been generally adopted, appeared to me much too great to 
admit of being referred to error of experiment. I was there- 
fore very anxious to return to the subject, and towards the 
end of July 1836, I undertook a fresh series of experiments, 
which were conducted on the following plan. 




H 



\. IAmm- 



r-nAf 



n t 



u 



;f>. 



A 



A pair of copper gasometers, A, B, with glass bells, C, D, 
such as are usually employed by chemical lecturers, were 
charged with a proper quantity of oil of vitriol, instead of 
water, and placed upon a table at the distance of three feet 
from each other, the brass caps, E, F, attached to the bells, 
being suspended to the extremities of a stout cord passing 
over a pair of pulleys, G, H, fixed in the ceiling of the la- 
boratory, the length of the cord being such that while one of 
the bells was almost entirely immersed in the oilof vitriol, the 
other dipped about an inch beneath its surface. Between the 
lower stopcocks, m, n, attached to the gasometers, a couple 
of glass tubes were interposed, connected to the stopcocks by 
caoutchouc collars, and fitting at their other extremities to 
each other by a tight ground joint. In the larger of these 
tubes the dry thermometer i was permanently placed, and into 
it the wet one t' was also introduced previous to the com- 
mencement of an experiment. Matters being, we shall sup- 
pose thus prepared, and the unimmersed bell, C, occupied, 



as deduced by himself and Dr. Suerman. 271 

first, with atmospherical air deprived by the oil of vitriol of 
it moisture, pressure was made upon it by an assistant, so as 
to force its contents in a rapid current into the second bell, 
D, through the tubes containing the wet and dry thermome- 
ters. During this operation the observer kept his eye, armed 
with a lens, steadily fixed on the thermometers, and registered 
the indications of both as soon as the wet one became and 
continued stationary for a kw seconds. The height of the 
barometer being now taken, the necessary data were obtained 
for calculating from formula (A), or 

fit - f _ ^1^ V P 

the elastic force of the vapour still existing in the air of the 
gasometer. This air being now replaced by one of the gases 
which were to be the subject of experiment, and this being 
left during the same time with the air in contact with the oil 
of vitriol, the very manipulations and observations just detailed 
were repeated. This same experiment was again and again 
performed, and it having been ascertained, after a consider- 
able number of repetitions, that the results were uniform and 
consistent, and that they might therefore be relied upon, the 
mean of all the observations was taken, and from this the spe- 
cific heat of the gas was deduced by means of the formula 

that value being assigned to /" which resulted from formula 
(A) applied to the preliminary experiments on atmospherical 
air. The analysis of the gas was next very carefully per- 
formed, and it having been ascertained that n volumes, e. g. 
of atmospherical air per cent, were present, the proper cor- 
rection was applied by the formula 

, ia — e)n 

a — a +-^ '— 

100— w 

already explained, in which e = '267 is the specific heat of 
air, a' the true specific heat of the gas, and a the specific 
heat of mixture of air and gas /as previously determined. 
Such was the course pursued in the case of each of the gases 
submitted to experiment. 

The particulars of the entire series of experiments are com- 
prehended in tables (1.) and (2.) Table (3.) contains the 
final results, alongside which are placed the numbers of De 
la Roche and Berard, and those of Dulong, for the purpose 
of comparison. 



272 Prof. Apjohn on the Specific Heats of the Gases, 

(1.) 



1836. 


t 


t' 


P 


d 


/" 


Aug. 8. 


63-5 


40-3 


23-2 


30-226 




8. 


63-2 


40-1 


231 


30-226 




8. 


63-2 


40 


23-2 


30-226 




Mean ... 


63-3 


40-1 


23-2 


30-226 


-0024 


Aug. 9. 


62-8 


40-5 


22-3 


30-250 




9. 


63 


40-8 


22-2 


30-250 




9. 


62-9 


40-6 


22-3 


30-250 




9. 


63-5 


4M 


22-4 


30-250 




9. 


63-2 


40-8 


22-4 


30-250 




Mean ... 


63-1 


40-7 


22-4 


30-250 


•0134 


Aug. 10. 


63 


40-7 


22-3 


30-208 




10. 


64 


41-5 


22-5 


30-208 




10. 


63-4 


41-2 


22-2 


30-208 




10. 


63-6 


10-9 


22-7 


30-208 




Mean ... 


63-5 


41-1 


22-4 


30-208 


•0114 


Aug. 11, 


62-2 


40-9 


21-3 


30-310 




11. 


63 


40-9 


22-1 


30-310 




11. 


63 


41-5 


21-5 


30-310 




11. 


63-8 


41-5 


22-3 


30-310 




11. 


63-2 


41-7 


21-5 


30-310 




11. 


63-2 


41-3 


21-9 


30-306 




11. 


64 


41-4 


22-6 


30-306 




Mean ... 


63-2 


41-3 


21-9 


30-307 


•0241 


Aug. 12. 


66-5 


41-8 


24-7 


30-270 


•0063 


15. 


65-8 


41-9 


23-9 


30-070 




15. 


66-5 


41-4 


25-1 


30-070 




15. 


66-6 


41-9 


24-7 


30070 




Mean ... 


66-3 


41-7 


24-6 


30-070 


•0027 



(2.) 



1836. 


t 


t' 


d 


P 


a 


Air 
percent 


a' 




^Aug. 8. 


62-5 


41-5 


21 


30-226 




10-2 






8. 


62-6 


41-5 


21-1 


30-226 










8. 


63 


41-9 


21-1 


30-226 








Carbonic Acid - 


8. 


63 


42-3 


20-7 


30-226 










8. 


63-6 


42-4 


21-2 


30-226 










8. 


63-7 


42-4 


21-3 


30-226 










L 8. 


63-2 


42-1 


21-1 


30-226 




11-4 




Mean ... 


63-1 


42 


21-1 


30-226 


•3136 


10-8 


•3992 


Hydrogen Aug. 8. 


63-6 


45-1 


18-5 


30-226 


•3970 


3-2 


-4012 




fAug. 9. 


62-1 


441 


18 


30-260 




3-2 






9. 


62-6 


44-1 


18-5 


30-260 




3-6 






9. 


63 


44-7 


18-3 


30-260 




4 




Hydrogen -■ 


9. 


62-8 


44-7 


18-1 


30-260 




4-4 






9. 


63 


44-6 


18-4 


30-260 




4-8 






9- 


63-8 


45-1 


18-7 


30-250 




5-2 






9. 


63 


44-6 


18-4 


30-250 




5-7 




Mean... 


62-9 


44-5 


18-4 


30-257 


•3734 


4-3 


•3781 


r Aug. 10. 


62-1 


42-1 


20 


30-200 




14- 




10. 


63 


42-4 


20-6 


30-205 








Nitrous Oxide ^ } J 


63-6 


42-6 


21 


30-210 








63 


42 


21 


30-210 








10. 


63-5 


42-5 


21 


30-210 








t 10. 


63-4 


42-6 


20-8 


30-210 




16 




Mean... 


63-1 


42-3 


20-8 30-207i-3109 


16 


3186 



as deduced bij himself and Dr. Suerman. 
TABLE (2) continued. 



273 



1836. 


t 


t' 


d 


;' 


a 




'"( 


Equal volumes 


fAug.ll. 


64-9 


42-8 


211 


30-306 








of Carb. Acid ■< 


11. 


65-4 


43-3 


22-1 


30-306 








and Carb. Oxide 


11- 


65-3 


43-3 


22 


30-306 










Mean... 


65-2 


43-1 


221 


30-306 


-2865 




•2865 


Equal volumes 


'Aug. 12. 


65-3 


42-7 


22-6 


30-27 








12. 


65-8 


43-4 


22-4 


30-27 








andCarb.Oxide 


12. 


65-8 


42-3 


23-5 


30-27 










12. 


65-3 


42-6 


22-7 


30-27 










Mean... 


65-5 


42-7 


22-8 


30-27 


-2988 




•2988 




rAug.15. 


64-8 


41-9 


22-9 


30-07 








Nitrogen ■< 


1 

1 


66-8 
66 


42-3 
42 


24-5 
24 


30-07 
30-07 










Mean... 


65-9 


42-1 


23-8 


30-07 


-2799 




•2799 



(3.) 



Specific Heats 


of equal 


Volumes. 




' 


J. A. 


De la Roche 

and 

Berard. 


Dulong. 


Atmospheric Air ... 

Nitrogen 

Oxygen 

Hydrogen 

Carbonic Acid .... 
Carbonic Oxide ... 
Nitrous Oxide 


•2670 
•2799 
•2154 
•3896 
•3192 
•2660 
•3186 


1-000 
1048 

•808 
1-459 
1195 

•996 
1-193 


1-000 

1-006 

•976 

•900 

r258 
1-034 
1-350 


1-000 
1-000 
1-000 
1-300 
1-172 
1-000 
1-159 



The number in this latter table for oxygen was inferred 
from that for nitrogen by formula (C), and the same may be 
said of the number attached to carbonic oxide, which was cal- 
culated in the same way from the specific heat of carbonic 
acid and of a mixture of equal volumes of the two gases, as 
deduced from experiment. From the care bestowed upon 
the various manipulations, and the consistency of the different 
observations in the same gas, I am disposed to look upon the 
numbers given above as very close approximations to the 
truth. I should probably except from this statement the spe- 
cific heats ascribed to oxygen and nitrogen, as but three ex- 
periments were made, in consequence of one of the gasometers 
having begun to leak. Moreover as nitrogen was the gas 
operated with, in passing by calculation to the specific heat of 
oxygen the errors of observation would be multiplied by four. 
Oxygen, in fact, not nitrogen, should have been the subject of 
experiment. 

[To be continued.] 

Phil, Mag. S, 3. Vol. 13. No. 82. Oct. 1838. T 



[ 274 ] 

XXXVII. A Remark on an Article of M. Poisson's Traite 
de Mecaniqiie {Edition 2nd. No. 593.). Bj/ James Ivory, 
K.H.,RR.S.,^c.* 

TN speculations of difficulty it is of great importance to note 
-*■ such points as are susceptible of clear demonstration. 
What is thus established by undoubted evidence, is not liable 
to be misapprehended or inadvertently misapplied. In this 
view it may be useful to demonstrate the following theorem, 
relating to the equilibrium of incompressible fluids, the par- 
ticles of which are urged by accelerating forces : If an in- 
terior level surface be extended through tJie mass, the hody of 
fluid isoithin the level surface 'will be in equilibrium independently 
of the rest of the mass, and supposing the incumbent fuid ivere 
removed. 

In order to demonstrate this theorem, suppose a canal 
to be conducted from an orifice in the upper surface of the 
fluid to the central point within all the level surfaces: the 
pressure of this canal at the centre, caused by all the forces 
which urge its elementary portions in the direction of the canal, 
and estimated on the unit of surface, will be the same, what- 
ever be the position of the initial point in the upper surface : 
the symbol B may be used to denote the intensity of the 
pressure at the centre resulting from this canal, which is no 
other than the central column of Newton. In like manner if 
a similar canal be drawn to the centre from any orifice in an 
interior level surface, the intensity of pressure at the centre, 
represented by b, will be a constant quantity. The intensity 
of the exterior pressure at all the points of the level surface, 
caused by all the forces that urge the particles of the incum- 
bent fluid, will be equal to B— ^. Using the same symbols 
as M. Poisson (Edition 2nd, No. 583), a;y, z will represent 
the three rectangular coordinates of a particle of the fluid ; 
X, Y, Z, the accelerating forces acting on the particle in the 
directions of a:,y,z; and, as unit may stand for the density 
of an incompressible fluid, we shall have 

B-b =f{Kdx + Ydy + Zdz) (a.) 

the integral representing the intensity with which any canal, 
having one orifice in the upper surface of the fluid and the 
other in the level surface, presses upon the level surface. 
By differentiating the equation, supposing the coordinates to 
vary in the level surface, we obtain 

Xdx + Ydy + Zdz = {b.) 

* Communicated by the Author. 



Mr. Ivorj's remark on a?i article hy M. Poisson. 275 

which expresses that the forces X, Y, Z are ineffective to dis- 
place the particles in any direction upon the level surface, 
their resultant being perpendicular to that surface. The sig- 
nification of these equations being explicitly settled, it readily 
follows that they are alone sufficient to determine the figure 
of equilibrium, when there are no other causes tending to 
displace a particle in a level surface, except the pressure of 
the incumbent fluid caused by all the forces, of whatever de- 
scription, that urge its particles. 

When the fluid consists of particles that attract one an- 
other, M. Poisson admits that the matter exterior to a level 
surface will attract the particles placed in that surface, or 
within it. The effect of this attractive force is perfectly di- 
stinct from the pressure of any canal passing between the 
upper surface and the level surface. In neither of the equa- 
tions (a) nor (i) is any account taken of an attraction which 
the exterior fluid exerts upon a particle in a level surface. 
But if the resultant of such attractions be not perpendicular 
to the level surface at every point, the particles in that sur- 
face will be displaced, and there will be no equilibrium. 
Let P, Q, R, represent the partial attractions of the matter 
exterior to a level surface, upon a particle in that surface, the 
forces being respectively parallel to .r, j/, s, the coordinates of 
the particle : then the condition that the attractive forces shall 
be ineffective to move the particle in any direction upon the 
level surface; or, which is the same thing, the condition that 
the resultant of the attractions shall be perpendicular to that 
surface, is thus expressed, 

/(Prf^ + Qr/j/ + R^;s= conSJ ^^'^ 

the coordinates varying in the level surface. Now these 
equations are not less indispensable than the former ones (a) 
and (b\ to the immobility of the particles of a level surface. 
And thus it appears that, when all the forces in action are taken 
into account, two independent conditions are necessary for 
determining the figure of equilibrium of a fluid at liberty, 
which consists of attracting particles; a conclusion that ac- 
cords perfectly with the result deduced from analytical con- 
siderations in this Journal for August last (p. 81). 

What has been proved is inconsistent with the argument 
of M. Poisson in the article (No. 593) cited from his Meca- 
7iiqjie. For, as it is here shown that the whole action of the 
exterior matter, whether by attraction or by pressure, upon 
the particles in a level surface, is directed perpendicularly to 
that surface, it follows that the removal of the exterior matter 

T2 



276 Mr. C. Binks on Electricity, 

will not alter the state of the fluid within the level surface 
with respect to an equilibrium. On the contrary, M. Poisson 
alleges that a necessary consequence of removing the exterior 
matter would be a change in the figure of the fluid body 
within the level surface. 

The discrepancy is easily explained. M. Poisson makes 
the equilibrium depend entirely on the equations {a) and {b) ; 
that is, he considers only the pressure of the exterior matter 
caused by the forces which urge its own particles, neglecting 
the attractive force of the same matter upon the interior fluid. 
When the effect of this attraction was pointed out, he gave 
the explanation of it in his work referred to. What he should 
have done was, to return upon his steps, and to correct his 
investigation by taking into account all the forces tending to 
move the particles of the fluid. 

A general demonstration of the theorem will readily sug- 
gest itself from what has been said. To elucidate the prin- 
ciple of the equality o/jpressure in all directiotis, and to point 
out what may safely be inferred from it, would exceed the 
present limits. 

Sept. 12, 1838. J. IvoRY. 

XXXVIII. Onsome of the PhcBnomena and La'ws of Action of 
Voltaic Electricity, and on the Constriictio7i of Voltaic Bat- 
tion,Sfc. By Christopher Binks. A second Cojumunica- 
teries, addressed to J. F. Daniell, Esq. F.R.S., S^c, Professor 
of Chemistry in King^s College, London. Part the First. 

[Continued from p. ISO.] 

159. A N examination of these results as they are shown by 
-^^ these tables, and by the diagram, would seem to 
warrant the following general inferences. 

160. 1st inference. That considering the zinc in these ar- 
rangements as the generating point, and the mass of liquid 
intermediate between it and the copper to be placed in an 
electrical condition, in whatever such a condition may consist, 
whether in the actual transmission through the liquid of a ma- 
terial agent, or the disposing of its particles into a state of po- 
larization, or of induction, or in what ; considering the elec- 
tricity developed at the zinc to exercise an influence of this 
nature over the intermediate mass, we must infer from these 
experiments, that that influence is diffiised over a greater 
space as we progressively recede fi'om the point from which 
it emanates, whilst its quantity, howsoever distributed, re- 
mains precisely the same. So that at the several distances of 



Voltaic Batteries, SjC* 277 

1, 2, and 4 inches above, we obtain this influence in the same 
amount, but find it to be distributed over spaces progressively 
increasing with the distance. 

161. Or the inference to be drawn from these facts may be 
otherwise expressed ; that the amount of electrical action oc- 
curring in such arrangements as those here employed, may be 
condensed within a smaller space, or diffused over a larger 
one, under certain limitations in both cases, in proportion as 
the elementary conducting plate is approached to, or removed 
from, the zinc or generating point, pi'esenting in these opera- 
tions a marked analogy to the general phaenomena of the ra- 
diation of light and heat. 

162. But in this kind of reasoning there are two assump' 
lions; first, that the zinc is the point from which this influ- 
ence emanates; and second, that the mass of liquid interposed 
between the two plates is placed in any peculiar condition ; 
and for neither of these have we the support of any direct evi- 
dence. 

163. Light and heat radiate in all directions from any ge- 
nerating point, as from one common centre. It matters not 
to the present purpose by what theory we explain the mode 
of emanation, or whether we assume their materiality or the 
contrary. We know of their presence at any given distance 
from the point of emanation, only by the interposition (as in 
the case of light), of any body capable of receiving its impres- 
sions, or of reflecting it; and in the case of heat, in like man- 
ner, only by the agency of some body interposed, and capable 
of appreciating or indicating its existence within the medium 
through which it is supposed to be diffused or propelled. The 
same agencies which serve to detect the presence of light and 
heat, serve also to measure their quantities. And in like man- 
ner does the copper-plate, in such voltaic arrangements as 
the above, serve to indicate the existence of voltaic action, 
and to measure its amount. The copper-plate may then be 
considered as subserving the same purpose in electrical ex- 
periments, as the screen in optical experiments, and the ther- 
mometer in those of heat ; but with this (though perhaps only 
apparent) difference, that the copper-plate is essential equally 
to the production as to the measurement of electricity ; whereas 
in the other two, their production is apparently independent 
of the instruments by which their quantities are determined. 
But making no attempt to trace the existence of any analogy 
as regards the way in which these several agents are originally 
produced, there seems, so far, to be some evidence for belie- 
ving, that when once produced, some of the phaenomena they 
exhibit are similar in general character ; and as far as regards 



278 Mr. C. Binks on Electricity, 

one such at least, namely, that of radiation, as far as that is 
developed in these experiments, the analogy between them 
appears to be complete. 

164. Reasoning upon the facts derived from experiment 
and by analogy, it thus appears that there is evidence for be- 
lieving that this divergence extends within the space bounded 
by the two plates ; but we have no experimental evidence 
that it extends in any other direction besides that thus deter- 
mined by the position of the conducting plate. It becomes a 
matter of importance to determine this point, that is, whether 
the electrical condition of the liquid is the same in every direc- 
tion around the zinc point, as it is in the direction of the cop- 
per plate ; or whether the direction of its influence is determined 
solely by the position of the copper ; and is entirely restricted 
to the mass of liquid interposed between it and the zinc, a 
question which appears to me to be finally determined by the 
investigations in sections 8 and 9. 

165. 2nd inference. That in the fact of this divergence, or 
this diffusion of tlie electrical influence over a space progress- 
ively increasing with the distance, we have afforded the means 
of explaining the decrease in amount of action which follows 
an increase in the relative distance of the two elementary plates, 
on a principle much more probably true than that to which 
this phsenomenon has generally been hitherto referred. It 
has generally been considered that this decrease is owing to 
the inferior conducting power of the greater mass of liquid 
interposed between the two plates. 

166. 3rd inference. From the above results we must con- 
clude, that the extent of this divergence is affected, in a cer- 
tain degree, by the particular strength of the acid mixture in 
which it takes place; for although every condition except that 
of the strength of the acid was maintained uniform in the two 
sets of experiments above, yet the dimensions of the plates, 
and the positions at which they are needed to produce the 
same effect, are different in each. The amount of this differ- 
ence is not great, nor can it be expected to be great ; but it 
is sufficiently marked to indicate that such an effect does re- 
sult from a difference in the particular strength of the mix- 
ture. But whether its immediate influence be due to the 
greater or less activity of the generating agents, or to the 
greater or less density of the acid mixture, or to whatever 
other cause, does not for the present appear. 

167. 4th inference. That the amount of voltaic action at 
certain points within such arrangements undergoes a pecu- 
liar change, which, in the present state of our knowledge of 
its operations generally, is equally unexpected and inexpli- 



Voltaic Batteries^ Sfc, 279 

cable. In some instances above, its amount is increased at 
certain positions, in others diminished, in cases in which, as 
yet, no apparent cause can be assigned for such an alteration. 
But the recurrence of this phaenomenon, with ft certain de- 
gree of regularity as to the positions at which it takes place, 
indicates that it has its origin in one uniform cause, the nature 
of which, however, so far, is wholly undetected. 

168. 5th inference. That in this alternation in the amount 
of action, which is detected by the larger plates used in the 
latter experiments to occur at several positions as we recede 
from the zinc or generating point, we perceive an effect pre- 
cisely similar, and in all probability identical with that already 
detected in the former experiments upon the effects of distance, 
as they were registered in tables, Nos. 5 and 6. The recur- 
rence of this alteration at similar positions in both cases, in- 
dicates that in the several instances it has its origin in one 
common cause, whatever that cause may be. 

169. I would not omit at this moment to remind you of the 
extent to which I consider myself indebted for a suggestion, 
which, in no inconsiderable degree, has influenced the reason- 
ing upon some of the facts derived from the previous experi- 
ments, though that suggestion did not originate the experi- 
ments themselves. You may remember that some time past, 
whilst urging me to follow up some former inquiries, you 
hinted it as your opinion that some phasnomena detected in 
them would prove ultimately to be due to radiation. 

Although this was the extent of your communication, and 
I was alike ignorant upon what grounds such a conjecture had 
been founded, and whether or not you had entered upon any 
investigations in accordance with it, yet an idea at once so 
novel and elegant could not fail to exercise its due influence 
upon any one then engaged in such pursuits. 

I am not prepared to say how far my own course of expe- 
rimenting already devised might have led to a similar train 
of I'easoning, since it is impossible that the mind could have 
been divested of the influence of such an impression thus in- 
cidentally conveyed. 

I need not say how fully I shall feel recompensed for the 
labour of experiment, if the results thus obtained independ- 
ently, shall be found in the end to be in accordance with 
your own views of the nature and extent of this phaenomenon, 
or shall agree with the results of any investigations of it upon 
which you may yourself have entered. 

1 70. My own results upon this point seem finally to indi- 
cate that this tendency to diverge is limited both in its extent 



280 Mr. C. Binks on Electricity^ Voltaic Batte7'ies, S;c, 

and direction ; and follows as a consequence of that law of ac- 
tion of voltaic arrangements stated in the previous part of this 
paper {section 1, 38, et seq.). 

171. I find that the electrical influence developed in such 
single arrangements, diffuses itself from the generating to the 
conducting metal to such an extent, and in such a manner, 
that it occupies upon the surface of the latter a space exactly 
thirty-two times greater than that engaged upon the former. 
This is a constant result in every such arrangement; and 
appears to depend upon the physical and chemical properties 
of the electrolyte; and to be entirely independent of the kind 
of metal employed in the arrangement. 

When the two metallic surfaces are in this proportion, then 
this diffusion upon the conducting surface, and the amount of 
action obtained in the arrangement, are at their maximum ; 
and when the conducting surface is made greater than this, 
then a singular change takes place, not only in degree (which 
is less), but also in the kind of action which results (see 
section 9). 

I find that the direction in which this divergence takes place 
is determined entirely by the position of the conducting sur- 
face. This surface may^be obtained by aplate of metal placed 
on one side of the generating point, or it may be so distri- 
buted as to be placed over against two or more of its sides, or 
it may be in the form of a holloxio cylinder or sphere, and be 
distributed entirely around the generating point; but what- 
ever may be its direction with relation to that point, or how- 
soever distributed, the direction in which this divergence from 
that point takes place is determined accordingly, and the 
amount of action resulting exactly the same. 

172. These effects are rendered obvious when the genera- 
ting point consists of a small solid sphere of zinc, and the 
conducting surface, first of a flat plate of copper thirty-two 
times larger and placed on one side; and then of an equal 
extent of surface distributed as a hollow sphere entirely 
around the zinc. By both is precisely the same amount of 
action obtained. By making either the plate or the sphere 
larger, we obtain no increase whatever of that amount ; but by 
reducing the extent of surface either of the sphere or the plate 
below this maximum size, then that amount is diminished in 
proportion and by the same rate in both cases. 

173. But there are other influences affecting the distribu- 
tion of the electricity when once generated in such arrange- 
ments. Some facts detected by experiment lead me to con- 
clude, that the direction which the electricity takes between 



Mr. Faraday's Exj^erimental Researches in Electricity. 281 

the two'elementary plates of any arrangement may be changed ; 
the nature of which change, and the circumstances under 
which it takes place, I proceed immediately to examine in the 
succeeding section. 

[To be continued.] 



XXXIX. Experimental Researches in Electricity. — Eleventh 
Series. By Michael Faraday, Esq.^ D.C.L.F.R.S. Ful- 
lerian Prof. Chem. Royal Institution^ Corr. Memb. Royal 
and Imp. Acadd. of Sciences, Par-is, Petershurgh, Florence, 
Copenhagen, Berlin, Sj-c. Sfc* 

§. 18. On Induction. ^ i. Induction an action of contiguous 
particles. ^ ii. Absolute charge of matter. ^ iii. Elec- 
trometer and inductive apparatus employed. % iv. Induc- 
tion in curved lines. % v. Specific i?iductive capacity. 
% vi. General results as to induction. 

% i. Induction an action of contiguous particles. 

1161. T^HE science of electricity is in that state in which 
•^ every part of it requires experimental investigation; 
not merely for the discovery of new effects, but, what is just 
now of far more importance, the development of the means 
by which the old effects are produced, and the consequent 
more accurate determination of the first principles of action 
of the most extraordinary and universal power in nature : — 
and to those philosophers who pursue the inquiry zealously 
yet cautiously, combining experiment with analogy, suspicious 
of their preconceived notions, paying more respect to a fact 
than a theory, not too hasty to generalize, and above all things, 
willing at every step to cross-examine their own opinions, 
both by reasoning and experiment, no branch of knowledge 
can afford so fine and ready a field for discovery as this. 
Such is most abundantly shown to be the case by the progress 
which electricity has made in the last thirty years: Chemistry 
and Magnetism have successively acknowledged its over- 
ruling influence ; and it is probable that every effect depend- 
ing upon the powers of inorganic matter, and perhaps most 
of those related to vegetable and animal life, will ultimately 
be found subordinate to it. 

1162. Amongst the actions of different kinds into which 
electricity has conventionally been subdivided, there is, I 
think, none which excels, or even equals in importance that 
called Induction. It is of the most general influence in elec- 
trical phaenomena, appearing to be concerned in every one of 
• From the Philosophical Transactions for 1838, Part I. 



282 Mr. Faraday's Experimental Researches in Electricity. 

them, and has in reality the character of a first, essential, and 
fundamental principle. Its comprehension is so important, 
that I think we cannot proceed much further in the investiga- 
tion of the laws of electricity without a more thorough under- 
standing of its nature; how otherwise can we hope to com- 
prehend the harmony and even unity of action which doubt- 
less governs electrical excitement by friction, by chemical 
means, by heat, by magnetic influence, by evaporation, and 
even by the living being ? 

1 163. In the long-continued course of experimental inquiry 
in which I have been engaged, this general result has pressed 
upon me constantly, namely, the necessity of admitting two 
forces, or two forms or directions of a force (516. 517.), 
combined with the impossibility of separating these two forces 
(or electricities) from each other, either in the phaenomena of 
statical electricity or those of the current. In association 
with this, the impossibility under any circumstances, as yet, 
of absolutely charging matter of any kind with one or the 
other electricity dwelt on my mind, and made me wish and 
search for a clearer view than any that I was acquainted with, 
of the way in which electrical powers and the particles of mat- 
ter are related ; especially in inductive actions, upon which 
almost all others appeared to rest. 

1164. When I discovered the general fact that electrolytes 
refused to yield their elements to a current when in the solid 
state, though they gave them forth freely if in the liquid con- 
dition (380. 394. 402.), I thought I saw an opening to the elu- 
cidation of inductive action, and the possible subjugation of 
many dissimilar phaenomena to one law. For let the electro- 
lyte be water, a plate of ice being coated with platina foil on 
its two surfaces, and these coatings connected with any con- 
tinued source of the two electrical powers, the ice will charge 
like a Leyden arrangement, presenting a case of common in- 
duction, but no current will pass. If the ice be liquefied, the 
induction will fall to a certain degree, because a current can 
now pass ; but its passing is dependent upon a peculiar mole- 
cular arrangement of the particles consistent with the transfer 
of the elements of the electrolyte in opposite directions, the 
degree of discharge and the quantity of elements evolved being 
exactly proportioned to each other (377. 783.). Whether 
the charging of the metallic coating be effected by a powerful 
electrical machine, a strong and large voltaic battery, or a 
single pair of plates, makes no difference in the principle, but 
only in the degree of action (360.). Common induction takes 
place in each case if the electrolyte be solid, or if fluid che- 
mical action and decomposition ensue, provided opposing ac- 



Ordinary Induction and Action of contiguous Particles. 283 

tions do not interfere ; and it is of high importance occasion- 
ally thus to compare effects in their extreme degrees, for the 
purpose of enabling us to comprehend the nature of an action 
in its weak state, which may be only sufficiently evident to us 
in its stronger condition. As, therefore, in the electrolyte, 
induction appeared to be the jirst step, and decomposition the 
second (the power of separating these steps from each other 
by giving the solid or fluid condition being in our hands) ; as 
the induction was the same in its nature as that through air, 
glass, wax, &c. produced by any of the ordinary means; 
and as the whole effect in the electrolyte appeared to be an 
action of the particles thrown into a peculiar or polarized 
state, I was led to suspect that common induction itself was 
in all cases an action of contiguous particles, and that electri- 
cal action at a distance (i. e. ordinary inductive action) never 
occurred except through the intermediate influence of the in- 
tervening matter. 

1165. The respect which I entertain towards the names of 
Epinus, Cavendish, Poisson, and other most eminent men, all 
of whose theories I believe consider induction as an action at 
a distance and in straight lines, long indisposed me to the 
view I have just stated ; and though I always watched for op- 
portunities to prove the opposite opinion, and made such ex- 
periments occasionally as seemed to bear directly on the point, 
as, for instance, the examination of electrolytes, solid and fluid, 
whilst under induction by polarized light (951, 955.), it is 
only of late, and by degrees, that the extreme generality of the 
subject has urged me still further to extend my experiments 
and publish my view. At present I believe ordinary induc- 
tion in all cases to be an action of contiguous particles, con- 
sisting in a species of polarity, instead of being an action of 
either particles or masses at sensible distances : and if this be 
true, the distinction and establishment of such a truth must 
be of the greatest consequence to our further progress in the 
investigation of the nature of electric forces. The linked con- 
dition of electrical induction with chemical decomposition ; 
of voltaic excitement with chemical action ; the transfer of 
elements in an electrolyte ; the original cause of excitement 
in all cases ; the nature and relation of conduction and insu- 
lation ; of the direct and lateral or transverse action consti- 
tuting electricity and magnetism ; with many other things 
more or less incomprehensible at present, would all be affected 
by it, and perhaps receive a full explication in their reduction 
under one general law. 

1166. I searched for an unexceptionable test of my view, 
not merely in the accordance of known facts with it, but in 



284 Mr. Faraday's Experimental Researches in Electricity. 

the consequences which would flow from it if true; especially 
in those which would not be consistent with the theory of ac- 
tion at a distance. Such a consequence seemed to me to pre- 
sent itself in the direction in which inductive action could be 
exerted. If in straight lines only, though not perhaps decisive, 
it would be against my view ; if in curved lines also, that would 
be a natural result of the action of contiguous particles, but I 
think utterly incompatible with action at a distance, as assumed 
by the received theories, which, according to every fact and 
analogy we are acquainted with, is always in straight lines. 

1167. Again, if induction be an action of contiguous par- 
ticles, and also the first step in the process of electrolyzation 
(lie^, 949.), there seemed reason to expect some particular 
relation of it to the different kinds of matter through which it 
would be exerted, or something equivalent to a specific elec- 
tric induction for different bodies, which, if it existed, would 
unequivocally prove the dependence of induction on the par- 
ticles; and though this, in the theory of Poisson and others, 
has never been supposed to be the case, I was soon led to 
doubt the received opinion, and have taken great pains in sub- 
jecting this matter to close experimental examination. 

1 168. Another ever-present question on my mind has been, 
whether electricity has an actual and independent existence 
as a fluid or fluids, or was a mere power of matter, like what 
we conceive of the attraction of gravitation. If determined 
either way it would be an enormous advance in our knowledge; 
and as having the most direct and influential bearing on my 
notions, I have always sought for experiments which would in 
any way tend to elucidate that great question. It was in at- 
tempts to prove the existence of electricity separate from mat- 
ter, by giving an independent charge of either positive or ne- 
gative povi'er to some substance, and the utter failure of all 
such attempts, whatever substance was used or whatever 
means of exciting or evolving electricity were employed, that 
first drove me to look upon induction as an action of the par- 
ticles of matter, each having both forces developed in it in ex- 
actly equal amount. It is this circumstance, in connexion 
with others, which makes me desirous of placing the remarks 
on absolute charge first, in the order of proof and argument, 
which I am about to adduce in favour of my view, that elec- 
tric induction is an action of the contiguous particles of the 
insulating medium or di-elcctric. 

5[ ii. On the absolute charge of matter, 

1169. Can matter, either conducting or non-conducting, 



On the absolute Charge of Matter. 285 

be charged with one electric force independently of the other y 
in the least degree, either in a sensible or latent state? 

1 1 70. The beautiful experiments of Coulomb upon the 
equality of action of conductors^ whatever their substance, and 
the residence of all the electricity upon their surfaces*, are 
sufficient, if properly viewed, to prove that conductors cannot 
he bodily charged; and as yet no means of communicating 
electricity to a conductor so as to relate its particles to one 
electricity, and not at the same time to the other in exactly 
equal amount, has been discovered. 

1171. With regard to electrics or non-conductors, the con- 
clusion does not at first seem so clear. They may easily be 
electrified bodily, either by communication (1247.) or excite- 
ment ; but being so charged, every case in succession, when 
examined, came out to be a case of induction, and not of ab- 
solute charge. Thus, glass within conductors could easily 
have parts not in contact with the conductor brought into an 
excited state ; but it was always found that a portion of the 
inner surface of the conductor was in an opposite and equiva- 
lent state, or that another part of the glass itself was in an 
equally opposite state, an inductive charge and not an absolute 
charge having been acquired. 

1172. Well-purified oil of turpentine, which I find to be 
an excellent liquid insulator for most purposes, was put into 
a metallic vessel, and, being insulated, was charged, sometimes 
by contact of the metal with the electrical machine, and at 
others by a wire dipping into the fluid within ; but whatever 
the mode of communication, no electricity of one kind was re- 
tained by the arrangement, except what appeared on the ex- 
terior surface of the metal, that portion being there only by 
an inductive action through the air around. When the oil of 
turpentine was confined in glass vessels, there were at first 
some appearances as if the fluid did receive an absolute charge 
of electricity from the charging wire, but these were quickly 
reduced to cases of common induction jointly through the 
fluid, the glass, and the surrounding air. 

1173. I carried these experiments on with air to a very 
great extent. I had a chamber built, being a cube of twelve 
feet in the side. A slight cubical wooden frame was constructed, 
and copper wire passed along and across it in various direc- 
tions, so as to make the sides a large net-work, and then all 
was covered in with paper, placed in close connexion with 
the wires, and supplied in every direction with bands of tin- 
foil, that the whole might be brought into good metallic com- 

• Mcmoires de I'Academie, 1786, pp. 67, 69, 72; 1787, p. 452. 



286 Mr. Faraday's Experimental Researches in Electricity. 

munication, and rendered a free conductor in every part. This 
chamber was insulated in the lecture-room of the Royal In- 
stitution; a glass tube above six feet in length was passed 
through its side, leaving about four feet within and two feet 
on the outside, and through this a wire passed from the large 
electrical machine (290.) to the air within. By working the 
machine, the air within this chamber could be brought into 
what is considered a highly electrified state (being, in fiict, the 
same state as that of the air of a room in which a powerful 
machine is in operation), and at the same time the outside of 
the insulated cube was everywhere strongly charged. But 
putting the chamber in communication with the perfect dis- 
charging train described in a former series (292.), and work- 
ing the machine so as to bring the air within to its utmost de- 
gree of charge, if I quickly cut off the connexion with the 
machine, and at the same moment or instantly after insulated 
the cube, the air within had not the least power to communi- 
cate a further charge to it. If any portion of the air was 
electrified, as glass or other insulators may be charged (1171.), 
it was accompanied by a corresponding opposite action 'within 
the cube, the whole effect being merely a case of induction. 
Every attempt to charge air bodily and independently with 
the least portion of either electricity failed. 

1174. I put a delicate gold-leaf electrometer within the 
cube, and then charged the whole by an outside communication, 
very strongly, for some time together ; but neither during the 
charge or after the discharge did the electrometer or air with- 
in show the least signs of electricity. I charged and discharged 
the whole arrangement in various ways, but in no case could 
I obtain the least indication of an absolute charge ; or of one 
by induction in which the electricity of one kind had the small- 
est superiority in quantity over the other. I went into the 
cube and lived in it, and using lighted candles, electrometers, 
and all other tests of electrical states, I could not find the least 
influence upon them, or indication of anything particular 
given by them, though all the time the outside of the cube 
was powerfully charged, and large sparks and brushes were 
darting off from every part of its outer surface. The conclu- 
sion I have come to is, that non-conductors, as well as con- 
ductors, have neveryet had an absolute and independent charge 
of one electricity communicated to them, and that to all ap- 
pearance such a state of matter is impossible. 

1 175. There is another view of this question which may be 
taken under the supposition of the existence of an electric 
fluid or fluids. It may be impossible to have the one fluid or 
State in a free condition without its producing by induction the 



No absolute Charge of Matter, — All Inductive. 287 

other, and yet possible to have cases in which an isolated por- 
tion of matter in one condition being uncharged, shall, by a 
change of state, evolve one electricity or the other: and though 
such evolved electricity might immediately induce the oppo- 
site state in its neighbourhood, yet the mere evolution of one 
electricity without the other in the Jlrst instance, would be a 
very important fact in the theory which assumes a fluid or 
fluids; these theories as I understand them assigning not the 
slightest reason why such an effect should not occur. 

1 176. But on searching for such cases I cannot find one. 
Evolution by friction, as is well known, gives both powers in 
equal proportion. So does evolution by chemical action, not- 
withstanding the great diversity of bodies which may be em- 
ployed, and ihe enormous quantity of electricity which can in 
this manner be evolved (371. 376. 861. 868,). The more 
promising cases of change of state, whether by evaporation, 
fusion, or the reverse processes, still give both forms of the 
power in equal proportion ; and the cases of splitting of mica 
and other crystals, the breaking of sulphur, &c. &c., are sub- 
ject to the same limitation. 

1 1 77. As far as experiment has proceeded, it appears, there- 
fore, impossible either to evolve or make disappear one elec- 
tric force without equal and corresponding change in the 
other. It is also equally impossible experimentally to charge 
a portion of matter with one electric force independently of 
the other. Charge always implies induction, for it can in no 
instance be effected without; and also the presence of the two 
forms of power, equally at the moment of development and 
afterwards. There is no absolute charge of matter with one 
fluid ; no latency of a single electricity. This though a nega- 
tive result is an exceedingly important one, being probably 
the consequence of a natural impossibility, which will become 
clear to us when we understand the true condition and theory 
of the electric power. 

1178. The preceding considerations already point to the 
following conclusions : bodies cannot be charged absolutely, 
but only relatively, and by a principle which is the same with 
thatof induction. AWchargeis sustained by induction. All phae- 
nomena of intensity include the principle of induction. All 
excitation is dependent on or directly related to induction. All 
currents involve previous intensity and therefore previous in- 
duction. Induction appears to be the essential function both 
in the first development and the consequent ph;enomena of 
electricity. 



288 Mr. Faraday's Experimental Researches in Electricity. 
^ iii. Electrometer and inductive apparatus employed. 

1179. Leaving for a time the further consideration of the 
preceding facts until they can be collated with other results 
bearing directly on the great question of the nature of induc- 
tion, I will now describe the appai'atus I have had occasion 
to use; and in proportion to the importance of the principles 
sought to be established is the necessity of doing this so clearly 
as to leave no doubt of the results behind. 

11 80. Electrometer. The measuring instrument I have em- 
ployed has been the torsion balance electrometer of Coulomb, 
constructed, generally, according to his instructions*, but with 
certain, variations and additions, which I will briefly describe. 
The lower part was a glass cylinder eight inches in height 
and eight inches in diameter ; the tube for the torsion thread 
was seventeen inches in length. The torsion thread itself was 
not of metal, but glass, according to the excellent suggestion 
of the late Dr. Ritchief. It was twenty inches in length, and 
of such tenuity that when the shell lac lever and attached ball, 
&c. were connected with it, they made about ten vibrations in 
a minute. It would bear torsion through four revolutions, or 
1440°, and yet, when released, return accurately to its po- 
sition ; probably it would have borne considerably more than 
this without injury. The repelled ball was of pith, gilt, and 
was 0*3 of an inch in diameter. The horizontal stem or lever 
supporting it was of shell lac, according to Coulomb's direc- 
tion, the arm carrying the ball being 2*4 inches long, and the 
other only 1*2 inches: to this was attached the vane, also de- 
scribed by Coulomb, which I found to answer admirably its 
purpose of quickly destroying vibrations. That the inductive 
action within the electrometer might be uniform in all posi- 
tions of the repelled ball and in all states of the apparatus, 
two bands of tin foil, about an inch wide each, were attached 
to the inner surface of the glass cylinder, going entirely round 
it, at the distance of 0*4 of an inch from each other, and at 
such a height that the intermediate clear surface was in the 
same horizontal plane with the lever and ball. These bands 
were connected with each other and with the earth, and, being 
perfect conductors, always exerted a uniform influence on the 
electrified balls within, which the glass surface, from its ir- 
regularity of condition at different times, I found, did not. 
For the purpose of keeping the air within the electrometer in 
a constant state as to dryness, a glass dish, of such size as to 
enter easily within the cylinder, had a layer of fused potash 

* Memoires de r Academic, 1785, p. 670. 
t Phil. Trans., 1830. 



CoulomU's Electrometer — particular Adjustments, 289 

placed within it, and this being covered with a disc of fine 
wire gauze to render its inductive action uniform at all pans, 
was placed within the instrument at the bottom and left 
there. 

1181. The moveable ball used to take and measure the por- 
tion of electricity under examination, and which may be called 
the repelling^ or the carrier, ball, was of soft alder wood, well 
and smoothly gilt. It was attached to a fine shell lac stem, 
and introduced through a hole into the electrometer accord- 
ing to Coulomb's method: the stem was fixed at its upper end 
in a block or vice, supported on three short feet : and on the 
surface of the glass cover above was a plate of lead with stops 
on it, so that when the carrier ball was adjusted in its right 
position, with the vice above bearing at the same time against 
these stops, it was perfectly easy to bring away the carrier 
ball and restore it to its place again very accurately, without 
any loss of time. 

1 182. It is quite necessary to attend to certain precautions 
respecting these balls. If of pith alone they are bad ; for 
when very dry, that substance is so imperfect a conductor 
that it neither receives nor gives a charge freely, and so, after 
contact with a charged conductor, is liable to be in an uncer- 
tain condition. Again, it is difficult to turn pith so smoothly 
as to leave the ball, even when gilt, sufficiently free from ir- 
regularities of form, as to retain its charge undiminished for 
a considerable length of time. When, therefore, the balls 
are finally prepared and gilt they should be examined, and 
being electrified, unless they can hold their charge with very 
little diminution for a considerable time, and yet be discharged 
instantly and perfectly by the touch of an uninsulated con- 
ductor, they should be dismissed. 

1183. It is, perhaps, unnecessary to refer to the graduation 
of the instrument, further than to explain how the observa- 
tions were made. On a circle or ring of paper on the outside 
of the glass cylinder, fixed so as to cover the internal lower 
ring of tin foil, were marked four points corresponding to an- 
gles of 90° ; four other points exactly corresponding to these 
points being marked on the upper ring of tin foil within. By 
these and the adjusting screws on which the whole instrument 
stands, the glass torsion thread could be brought accurately 
into the centre of the instrument and of the graduations on 
it. From one of the four points on the exterior of the cylin- 
der a graduation of 90° was set off", and a corresponding gra- 
duation was placed upon the upper tin foil on the opposite 
side of the cylinder within ; and a dot being marked on that 
point of the surface of the repelled ball nearest to the side of 

Phil, Mag. S. 3. Vol. 13. No. 82. Oct, 1838. U 



290 Mr. Faraday's Experimental Researches in Electricity, 

the electrometer, it was easy, by observing the line which this 
dot made with the lines of the two graduations just referred 
to, to ascertain accurately the position of the ball. The upper 
end of the glass thread was attached, as in Coulomb's original 
electrometer, to an index, which had its appropriate graduated 
circle, upon which the degree of torsion was ultimately to be 
read off. 

1184. After the levelling of the instrument and adjustment 
of the glass thread, the blocks which determine the place of 
the carrier- ball are to be regulated (1181.) so that, when the 
carrier arrangement is placed against them, the centre of the 
ball may be in the radius of the instrument corresponding to 
0° on the lower graduation or that on the side of the electro- 
meter, and at the same level and distance from the centre as 
the repelled ball on the suspended torsion lever. Then the 
torsion index is to be turned until the ball connected with it 
(the repelled ball) is accurately at 30°, and finally the gra- 
duated arch belonging to the torsion index is to be adjusted so 
as to bring 0° upon it to the index. This state of the instru- 
ment was adopted as that which gave the m(5st direct expres- 
sion of the experimental results, and in the form having few- 
est variable errors ; the angular distance of 30° being always 
retained as the standard distance to which the balls were in 
every case to be brought, and the whole of the torsion being 
read off at once on the graduated circle above. Under these 
circumstances the distance of the balls from each other was 
not merely the same in degree, but their position in the in- 
strument, and in relation to every part of it, was actually the 
same every time that a measurement was made ; so that all 
irregularities arising from slight difference of form and action 
in the instrument and the bodies around were avoided. The 
only difference which could occur in the position of anything 
within, consisted in the deflexion of the torsion thread from a 
vertical position, more or less, according to the force of re- 
pulsion of the balls ; but this was so slight as to cause no in- 
terfering difference in the symmetry of form within the in- 
strument, and gave no error in the amount of torsion force 
indicated on the graduation above. 

1185. Although the constant angular distance of 30° be- 
tween the centres of the balls was adopted, and found abun- 
dantly sensible, for all ordinary purposes, yet the facility of 
rendering the instrument far more sensible by diminishing 
this distance was at perfect command; the results at different 
distances being very easily compared with each other either 
by experiment, or, as they are inversely as the squares of the 
distances, by calculation. 



Induction Apparatus described. 291 

1186. The Coulomb balance electrometer requires expe- 
rience to be understood ; but I think it a very valuable instru- 
ment in the hands of those who will take pains by practice and 
attention to learn the precautions needful in its use. Its insu- 
lating condition varies with circumstances, and should be ex- 
amined before it is employed in experiments. In an ordinary 
and fair condition, when the balls were so electrified as to give 
a repulsive torsion force of 400° at the standard distance of 30°, 
it took nearly four hours to sink to 50° at the same distance ; 
the average loss from 400° to 300° being at the rate of 2°*7 
per minute, from 300° to 200° of l°-7 per minute, from 200° 
to 100° of l°-3 per minute, and from 100° to 50° of 0°'87 per 
minute. As a complete measurement by the instrument may 
be made in much less than a minute, the amount of loss in 
that time is but small, and can easily be taken into account. 

1 187. The inductive apparatus. — My object was to examine 
inductive action carefully when taking place through different 
media, for which purpose it was necessary to subject these 
media to it in exactly similar circumstances, and in such quan- 
tities as should suffice to eliminate any variations they might 
present. The requisites of the apparatus to be constructed 
were, therefore, that the inducing surfaces of the conductors 
should have a constant form and state, and be at a constant 
distance from each other ; and that either solids, fluids, or 
gases might be placed and retained between these surfaces 
with readiness and certainty, and for any length of time. 

1188. The apparatus used may be described in general 
terms as consisting of two metallic spheres of unequal diame- 
ter, placed, the smaller within the larger, and concentric with 
it; the interval between the two being the space through 
which the induction was to take place. A section of it is 
given (fig. 1.) on a scale of one third: a, «, are the two 
halves of a brass sphere, with an air-tight joint at b, like that 
of the Magdeburg hemispheres, made perfectly flush and 
smooth inside so as to present no irregularity ; c is a connect- 
ing piece by which the apparatus is joined to a good stop-cock 
df which is itself attached either to the metallic foot e, or to 
an air pump. The aperture within the hemisphere aty is very 
small : ^ is a brass collar fitted to the upper hemisphere, 
through which the shell lac support of the inner ball and its 
stem passes ; h is the inner ball, also of brass ; it screws on to 
a brass stem i, terminated above by a brass ball B ; /, / is a 
mass of shell lac, moulded carefully on to i, and serving both 
to support and insulate it and its balls h, B. The shell-lac 
stem I is fitted into the socket g, by a little ordinary resinous 
cement, more fusible than shell-lac, applied atmmin such a 

U2 



Fig. 



292 Mr. Faraday's Experimental Researches in Electricity, 

way as to give sufficient strength and render tiie apparatus air- 
tight there, yet leave as much 
as possible of the lower part of 
the shell-lac stem untouched, 
as an insulation between the 
ball h and the surrounding 
sphere a, a. The ball h has 
a small aperture at n, so that 
when the apparatus is exhaust- 
ed of one gas and filled with 
another, the ball h may itself 
also be exhausted and filled, 
that no variation of the gas in 
the interval o may occur du- 
ring the course of an experi- 
ment. 

1189. It will be unnecessary 
to give the dimensions of all 
the parts, since the drawing 
is to a scale of one third : the 
inner ball has a diameter of 
2'33 inches, and the surround- 
ing sphereaninternaldiameter 
of 3*57 inches. Hence the 
width of the intervening space, 
through which the induction 
is to take place, is 0*62 of an 
inch ; and the extent of this 
place or plate, i. e. the surface of 
a medium sphere, maybe taken 
as twenty-seven square inches, a quantity considered as suffi- 
ciently large for the comparison of different substances. Great 
care was taken in finishing well the inducing surfaces of the 
ball h and sphere a, a; and no varnish or lacquer was applied 
to them, or to any part of the metal of the apparatus. 

1190. The attachment and adjustment of the shell-lac stem 
was a matter requiring considerable care, especially as, in con- 
sequence of its cracking, it had frequently to be renewed. 
The best lac was chosen and applied to the wire /, so as to 
be in good contact with it everywhere, and in perfect conti- 
nuity throughout its own mass. It was not thinner than is 
given by scale in the drawing, for when less it frequently 
cracked within a few hours after its cooling. I think that 
very slow cooling or annealing improved its quality in this re- 
pect. The collar ^ was made as thai as could be, that the 




Jac might be as large there as possible. In order that at every 



Itidmtion Apparatus described, 293 

re-attachment of the stem to the upper hemisphere the ball h 



Fig. 2. 




mmm 



might have the same relative posi 
tion, a gauge p (fig. 2.) was made of 
wood, and this being applied to the 
ball and hemisphere whilst the ce- 
ment at m was still soft, the bearings 
of the ball at q </, and the hemisphere 
at r r, were forced home, and the 
whole left until cold. Thus all diffi- 
culty in the adjustment of the ball in 
the sphere was avoided. 

1191. I had occasion at first to 
attach the stem to the socket by other 
means, as a band of paper or a 
plugging of white silk thread ; but 
these were very inferior to the ce- 
ment, interfering much with the in- 
sulating power of the apparatus. 

1 192. The retentive power of this 
apparatus was, when in good condi- 
tion, better than that of the electro- 
meter (1 186.), i.e. the proportion of loss of power was less. Thus 
when the apparatus was electrified, and also the balls in the elec- 
trometer, to such a degree, that after the inner ball had beenin 
contact with the top k of the ball of the apparatus, it caused a 
repulsion indicated by 600° of torsion force, then in falling 
from 600° to 400° the average loss was 8°'6 per minute; from 
400° to 300° the average loss was 2°*6 per minute ; from 300° 
to 200° it was l°-7 per minute; from 200° to 170° it was 1° 
per minute. This was after the apparatus had been charged 
for a short time ; at the first instant of charging there is an 
apparent loss of electricity, which can only be comprehended 
hereafter (1207. 1250.). 

1193. When the apparatus loses its insulating power sud- 
denly, it is almost always from a crack near to or within the 
brass socket. These cracks are usually transverse to the 
stem. If they occur at the part attached by common cement 
to the socket, the air cannot enter, and being then as vacua, 
they conduct away the electricity and lower the charge, as 
fast almost as if a piece of metal had been introduced there. 
Occasionally stems in this state, being taken out and cleared 
from the common cement, may, by the careful application of 
the heat of a spirit lamp, be so far softened and melted as to 
renew perfect continuity of the parts; but if that does not 
succeed in restoring things to a good condition, the remedy is 
a new shell-lac stem. 



294) Mr. Faraday's Experimental Researches in Electricity. 

1194;. The apparatus when in order could easily be ex- 
hausted of air and filled with any given gas ; but when that 
gas was acid or jtlkaline, it could not properly be removed by 
the air-pump, and yet required to be perfectly cleared away. 
In such cases the apparatus was opened and cleared; and 
with respect to the inner ball ^, it was washed out two or 
three times with distilled water introduced at the screw hole, 
and then being heated above 212°, air was blown through to 
render the interior perfectly dry. 

1195. The inductive apparatus described is evidently a 
Leyden phial, with the advantage, however, of having the di- 
electric or insulating medium changed at pleasure. The balls 
h and B, with the connecting wire i, constitute the charged 
conductor, upon the surface of which all the electric force is 
resident by virtue of induction (1178.). Now though the 
largest portion of this induction is between the ball h and the 
surrounding sphere a a, yet the wire i and the ball B deter- 
mine a part of the induction from their surfaces towards the 
external surrounding conductors. Still, as all things in that 
respect remain the same, whilst the medium within at o o, may 
be varied, any changes exhibited by the whole apparatus will 
in such cases depend upon the variations made in the interior ; 
and it was these changes I was in search of, the negation or 
establishment of such dijfFerences being the great object of my 
inquiry. I considered that these differences, if they existed, 
would be most distinctly set forth by having two apparatus of 
the kind described, precisely similar in every respect; and 
then, different insulating media being within, to charge one 
and measure it, and after dividing the charge with the other, 
to observe what the ultimate conditions of both were. If in- 
sulating media really had any specific differences in favouring 
or opposing inductive action through them, such differences, 
I conceived, could not fail of being developed by such a pro- 
cess. 

1196. I will wind up this description of the apparatus, and 
explain the precautions necessary in their use, by describing 
the form and order of the experiments made to prove their 
equality when both contained common air. In order to fa- 
cilitate reference I will distinguish the two by the terms App. 
i, and App. ii. 

1 197. The electrometer is first to be adjusted and examined 
(1184.), and the app. i. and ii. are to be perfectly discharged. 
A Leyden phial is to be charged to such a degree that it would 
give a spark of about one-sixteenth or one-twentieth of an inch 
in length between two balls of half an inch diameter ; and the 
carrier ball of the electrometer being charged by this phial, is 



Induction Apparatus. — Precautions in its use. 295 

to be introduced into the electrometer, and the lever ball 
brought by the motion of the torsion index against it ; the 
charge is thus divided between the balls, and repulsion ensues. 
It is useful then to bring the repelled ball to the standard di- 
stance of 30° by the motion of the torsion index, and observe 
the force in degrees required for this purpose ; this force will 
in future experiments be called rcpulsioji of the halls. 

1198. One of the inductive apparatus, as for instance, app, 
i., is now to be charged from the Leyden phial, the latter 
being in the state it was in when used to charge the balls ; 
the carrier ball is to be brought into contact with the top of 
its upper ball {k, fig. 1.), then introduced into the electrome- 
ter, and the repulsive force (at the distance of 30°) measured. 
Again, the carrier should be applied to the app. i. and the 
measurement repeated ; the apparatus i. and ii. are then to be 
joined, so as to divide the charge, and afterwards the force of 
each measured by the carrier ball, applied as before, and the 
results carefully noted. After this both i. and ii. are to be 
discharged ; then app. ii. charged, measured, divided with 
app. i., and the force of each again measured and noted. If 
in each case the half charges of app. i. and ii. are equal, and 
are together equal to the whole charge before division, then it 
may be considered as proved that the two apparatus are pre- 
cisely equal in power, and fit to be used in cases of comparison 
between different insulating media or dielectrics. 

1199. But the precautions necessary to obtain accurate re- 
sults are numerous. The apparatus i. and ii. must always be 
placed on a thoroughly uninsulating medium. A mahogany 
table, for instance, is far from satisfactory in this respect, and 
therefore a sheet of tin foil, connected with an extensive dis- 
charging train (292.), is what I have used. They must be so 
placed also as not to be too near each other, and yet equally 
exposed to the inductive influence of surrounding objects ; and 
these objects, again, should not be disturbed in their position 
during an experiment, or else variations of induction upon 
the external ball B of the apparatus may occur, and so errors 
be introduced into the results. The carrier ball, when re- 
ceiving its portion of electricity from the apparatus, should 
always be applied at the same part of the ball, as, for instance, 
the summit ^, and always in the same way ; variable induction 
from the vicinity of the head, hands, &c. being avoided, and 
the ball after contact being withdrawn upwards in a regular 
and constant manner. 

1200. As the stem had occasionally to be changed (1190.), 
and the change might occasion slight variations in the position 
of the ball within, I made such a variation purposely, to the 



296 Mr. Faraday's Experimental Researches in Electricity. 

aqjount of an eighth of an inch (which is far more than ever 
could occur in practice), but did not find that it sensibly altered 
the relation of the apparatus, or its inductive condition as a 
nxsJiole. Another trial of the apparatus was made as to the 
effect of dampness in the air, one being filled with very dry 
air, and the other with air from over water. Though this 
produced no change in the result, except an occasional tend- 
ency to more rapid dissipation, yet the precaution was always 
taken when working with gases (1290.) to dry them per- 
fectly. 

1201. It is essential that the interior of the apparatus should 
hQ perfectly free from dust or small loose particles, for these 
very rapidly lower the charge and interfere on occasions when 
Iheir presence and action would hardly be expected. To 
bi-eathe on the interior of the apparatus and wipe it out quietly 
with a clean silk handkerchief, is an effectual way of removing 
them ; but then the intrusion of other particles should be care- 
fully guarded against, and a dusty atmosphere should for this 
and several other reasons be avoided. 

1202. The shell lac stem requires occasionally to be well 
wiped, to remove, in the first instance, the film of wax and 
adhering matter which is upon it ; and afterwards to displace 
dirt and dust which will gradually attach to it in the course 
of experiments. I have found much to depend upon this pre- 
caution, and a silk handkerchief is the best wiper. 

1203. But wiping and some other circumstances tend to 
give a charge to the surface of the shell lac stem. This should 
be removed, for, if allowed to remain, it very seriously affects 
the degree of charge given to the carrier ball by the apparatus 
(1232.). This condition of the stem is best observed by dis- 
charging the apparatus, applying the carrier ball to the stem, 
touching it with the finger, insulating and removing it, and 
examining whether it has received any charge (by induction) 
from the stem ; if it has, the stem itself is in a charged state. 
The best method of removing the charge I have found to be, 
to cover the finger with a single fold of a silk handkerchief, and 
breathing on the stem, to wipe it immediately after with the 
finger, the ball B and its connected wire, &c. being at the 
same time uninsulated', the wiping place of the silk must not 
be changed ; it then becomes sufficiently damp not to excite 
the stem, and is yet dry enough to leave it in a clean and ex- 
cellent insulating condition. If the air be dusty, it will be 
found that a single charge of the apparatus will bring on an 
electric state of the outside of the stem, in consequence of the 
carrying power of the particles of dust ; whereas in the morn- 
ing, and in a room which has been left quiet, several experl- 



Induction Apparatus. — Mode ofdividijig charges. 297 

ments can be made in succession without the stem assuming 
the least degree of charge. 

1204. Experiments should not be made by candle or lamp 
light except with much care, for flames have great and yet 
unsteady powers of affecting and dissipating electrical charges. 

1205. As a final observation on the state of the apparatus, 
they should retain their charge well and uniformly, and alike 
for both, and at the same time allow of a perfect and instant- 
aneous discharge, giving them no charge to the carrier ball, 
whatever part of the ball B it may be applied to (1218.). 

1206. With respect to the balance electrometer all the pre- 
cautions that need be mentioned, are, that the carrier ball is 
to be preserved during the first part of an experiment in its 
electrified state, the loss of electricity which would follow upon 
its discharge being avoided ; and, that in introducing it into 
the electrometer through the hole in the glass plate above, 
care should be taken that it do not touch, or even come near 
to, the edge of the glass. 

1207. When the whole charge in one apparatus is divided 
between the two, the gradual fall, apparently from dissipation, 
in the apparatus which has received the half charge is greater 
than in the one originally charged. This is due to a peculiar 
effect to be described hereafter (1250. 1251.), the interfering 
influence of which may be avoided to a great extent by going 
through the steps of the process regularly and quickly ; there- 
fore, after the original charge has been measured, in app. i. 
for instance, i. and ii. are to be symmetrically joined by their 
balls B, the carrier touching one of these balls at the same 
time ; it is first to be removed, and then the apparatus sepa- 
rated from each other ; app. ii. is next quickly to be measured 
by the carrier, then app. i. ; lastly, ii. is to be discharged, and 
the discharged carrier applied to it to ascertain whether any 
residual effect is present (1205.), and app. i. being discharged 
is also to be examined in the same manner and for the same 
purpose. 

1208. The following is an example of the division of a 
charge by the two apparatus, air being the dielectric in both 
of them. The observations are set down one under the other 
in the order in which they were taken, the left hand numbers 
representing the observations made on app. i. and the right 
hand numbers those on app. ii. App. i. is that which was 
ori finally charged, and after two measurements, the charge 
was divided with app. ii. 

App. i. App. ii. 

Balls 160° 

0° 



298 Mr. Faraday's Experimental Researches in Electricity. 

App. i. App. ii. 

254° 

250 

divided and instantly taken 

122 

124. 

1 after being discharged. 

2 after being discharged. 

1209. Without endeavouring to allow for the loss which 
must have been gradually going on during the time of the ex- 
periment, let us observe the results of the numbers as they 
stand. As 1° remained in app. i. in an undischargeable state, 
249° may be taken as the utmost amount of the transferable 
or divisible charge, the half of which is 124°'5. As app. ii. 
was free of charge in the first instance, and immediately after 
the division was found with 122°, this amount at least may be 
taken as what it had received. On the other hand 124° minus 
1°, or 123°, may be taken as the halfofthe transferable charge 
retained by app. i. Now these do not differ much from each 
other, or from 124°'5, the half of the full amount of transfer- 
able charge; and when the gradual loss of charge evident in 
the difference between 254° and 250" of app. i. is also taken 
into account, there is every reason to admit the result as show- 
ing an equal division of charge, unattended by any disappear- 
ance qf power except that due to dissipation. 

1210. I will give another result, m which app. ii. was first 
charged, and where the residual action of that apparatus was 
greater than in the former case. 

App. i. App. ii. 

Balls 150° 

152" 

148 

divided and instantly taken 

70° 

78 

5 immediately after discharge. 

immediately after discharge. 

1211. The transferable charge being 148° — 5°, its half is 
71°'5, which is not far removed from 70°, the half charge of 
i. ; or from 73°, the half charge of ii. : these half charges again 
making up the sum of 143°, or just the amount of the whole 
transferable charge. Considering the errors of experiment, 
therefore, these results may again be received as showing that 
the apparatus were equal in inductive capacity, or in their 
powers of receiving charges. 

1212. The experiments were repeated with charges of ne- 
gative electricity with the same general results. 



Geological Society, 299 

1213. That I might be sure of the sensibility and action of 
the apparatus, I made such a change in one as ought upon 
principle to increase its inductive force, i. e. I put a metallic 
lining into the lower hemisphere of app. i., so as to diminish 
the thickness of the intervening air in that part, from 062 to 
O'^SS of an inch : this lining was carefully shaped and rounded 
so that it should not present a sudden projection within at its 
edge, but a gradual transition from the reduced interval in the 
lower part of the sphere to the larger one in the upper. 

1214. This change immediately caused app. i. to produce 
effects indicating that it had a greater aptness or capacity for 
induction than app. ii. Thus, when a transferable charge in 
app. ii. of 469° was divided with app. i., the former retained 
a charge of 225°, whilst the latter showed one of 227°, i. e. 
the former had lost 24'4° in communicating 227° to the latter : 
on the other hand, when app. i. had a transferable charge in 
it of 381° divided by contact with app. ii., it lost 181° only, 
whilst it gave to app. ii. as many as 194°: — the sum of the di- 
vided forces being in the first instance less^ and in the second 
instance greater than the original undivided charge. These 
results are the more striking, as only one half of the interior 
of app. i. was modified, and they show that the instruments 
are capable of bringing out differences in inductive force from 
amongst the errors of experiment, when these differences are 
much less than that produced by the alteration made in the 
present instance. 

[To be continued.] 

XL. Proceedings of Learned Societies. 

GEOLOGICAL SOCIETY. 
[Continued from p. 233.] 

May 23. — A memoir entitled, a Synopsis of the English series of 
stratified rocks inferior to the old red sandstone — with an attempt 
to determine the successive natural groups and formations, by the 
Rev. Adam Sedgwick, Woodwardian Professor in the University of 
Cambridge, commenced on the 21st March, was concluded. 

Introduction. — The author, after stating what was now oflpiered to 
the Society to be only a first approximation, involving many questions 
of difficulty and doubt, pointed out the principles on which he had 
undertaken the task. There are two elements of classification ap- 
l)licable to stratified rocks of all ages, viz., physical structure and 
order of superposition; one giving the mineralogical unity of a 
group of rocks, the other their relative age. In addition to the two 
former, are classifications founded on the organic remains in the 
several groups. In the commencement of geology the last method 
was only subsidiary to the two former. But after observations had 



300 Geological Society : Prof. Sedgwick on the 

been multiplied, laws respecting the distribution of organic types 
were discovered, which not merely superseded, in many large for- 
mations, all classifications founded on mineral structure ; but often, 
through wide regions, gave indications of succession which were 
unsupported by the direct evidence of sections. As, however, the 
(so called) laws respecting the distribution of organic types, are 
mere general results grounded on actual observation, it is obvious 
that they can never upset conclusions drawn from the clear and un- 
ambiguous evidence of sections. The two methods may be used 
independently, and conspire to the same end ; but in their nature 
cannot come into permanent collision. 

The author then points out some examples in which these principles 
had been violated. (1) The attempt formerly made by some geolo- 
gists to arrange the Stonesfield slate in a tertiary group, merely from 
the presence of certain fossils of a class not commonly found in second- 
ary rocks. (2) Some of the doctrines put forth in the papers of M. 
Deshayes, which if pushed to their utmost extent would make the 
evidence of sections of no value ; whereas without sections fossils 
could never have led to any general laws of succession. (3) The 
recent discussions respecting the age of the culm plants of North 
Devon. The plants were assumed to be of the age of the greywacke, 
from the mineral structure of the rocks in which they were imbedded ; 
or the rocks were assumed to be of the carboniferous period by the 
species of the imbedded plants : whereas true geological reasoning 
required that, anterior to either of the preceding conclusions, the 
true position of the culm measures should be determined by actual 
sections. 

The author then goes on to point out the difficulty of classify- 
ing the vast series of schistose rocks below the old red sandstone 
— from the great resemblance of their mineral type — from the 
absence of well-defined beds of organic remains in many large re- 
gions — and from their entire disappearance in the last members 
of the descending series. The Silurian system is almost the only 
exception to this remark ; and even this system is developed 
in many parts of England without any distinct succession of natural 
groups. The mineral type is on the whole much more uniform in the 
great series under notice than in the secondary system of England ; 
but the frequent absence of organic remains, and of any succession 
of distinct groups, is compensated by the enormous scale of deve- 
lopment, as shown in the natural sections : and the author concludes, 
that it is not by hypothetical views and analogies, or by maintaining 
one part of geological evidence at the expense of another ; but by 
applying every kind of evidence in its proper place, and above all by 
actual surveys and detailed sections, that we can ever hope to bring 
into coordination the complicated phaenomena of which he is only 
attempting to give a brief synopsis. 

TWO CLASSES OF OLD STRATIFIED ROCKS, &C. 

The author first notices the older stratified series of Scotland, and 
divides it into two classes. 



English Stratified BocJcs inferior to the Old Red Sandstone, 301 

(1.) The primary class (composed of gneiss, mica slate, quartz 
rock, &c. &c.,) is largely developed in the Highlands. 

(2.) The second class (greywack6, greywackd alate, &c. &c,,) is 
also largely developed in the Lammermuir hills, and in the whole 
chain extending in the south of Scotland from St. Abb's Head to 
the Mull of Galloway. It is shown, partly on mineralogical cha- 
racters, and partly on the evidence of sections, that the rocks of the 
former class are inferior to those of the latter. For a zone of slate 
rocks (the roches chloriteuses et quarizeuses of Dr. Boue) is superior 
to the crystalline slates of the Grampians, and is (at least pro- 
visionally) placed on the same parallel with the earthy and me- 
chanical slates of the Lammermuir chain. Both the preceding classes 
are shown to be inferior, and generally unconformable, to the old red 
sandstone ; which in the northern part of Scotland was once grouped 
with the primary class ; but in the geological map of Scotland is now 
jiut in its true place. 

After giving a series of sections to connect the structure of the 
Lammermuir chain with the adjacent parts of the north of England, 
he then proceeds to describe, in general terms, the expansion of the 
rocks of the second class through various mountainous tracts of 
South Britain. The frontier chain of Scotland — the slaty series of 
the Cumbrian mountains — of North and South Wales — and of the 
whole region between the eastern side of Devon and the western end 
of Cornwall — as well as the slate rocks of some smaller unconnected 
tracts, are all referred to one great class, the highest group of which 
passes into the old red sandstone, while the lowest (where the de- 
velopment is complete) rests on the crystalline system of the first 
class. Independently of the direct evidence from detailed sections, 
the several regions are shown to be related ; 1st, by a common phy- 
sical structure ; 2ndly, by organic remains ; 3dly, by common lines 
of strike ; tending to show that several disconnected tracts of wide 
extent, having partaken of the same accidents, were once probably 
connected and continuous deposits in a deep sea. 

In illustration of these views he shows that the prevailing strike 
of the beds (as well as the prevailing direction of the anticlinal and 
synclinal lines) in the Lammermuir system, in the Cumbrian system, 
and in the system of all the highest chains of North Wales, is nearly 
N.E. and S.W. and he further shows that the actual impress was 
given to all these regions before the period of the old red sandstone. 
In Cornwall the average strike is about W.N.W., but gradually 
bends round- to the E. and W., in which prevailing direction the 
rocks cross Devonshire. In the southern parts of the slate regions 
of South Wales the beds also have an east and west strike ; and 
these parallel dislocations of Devonshire and South Wales are pos- 
terior to the carboniferous series and probably contemporaneous with 
one another. Where the two preceding systems of strike meet, the 
beds are thrown into inextricable confusion ; and on the outskirts of 
Wales, and in the counties where the Silurian system has been most 
largely developed, the dislocations are too irregular and complicated 
to be reduced to any law. Lastly, he notices a system of dislocations 



802 Geological Society: Prof. Sedgwick on the 

that have brought up a portion of the older rocks (of the class here 
described) at Dudley, on both sides of the Warwickshire coal field, 
and in Charnwood forest. At all these localities the strike is the 
same, and the lines of greatest movement are nearly parallel — all being 
about N.N.W. and S.S.E. ; and all these movements belong to one 
epoch, having been completed after the deposition of the lower red 
sandstone, and before the period of the upper and gypseous marls. 
Hence we have three great systems of elevation, each marked by 
parallel lines of strike, and the three systems of strike indicating 
three distinct periods of elevation. 

The author then points out the importance of such facts to the 
broad speculations of geology, as well as the limitations under which 
they are to be applied. The dynamical powers of elevation appear 
to have been employed in three principal forms. 1st. In gradually 
raising up ridges through large spaces of the earth's crust. These 
will explain the correspondence of strike through very extensive 
regions ; and such elevations if continued beyond a certain limit must 
have produced longitudinal fissures and lines of volcanic vent. 2ndly. 
In the long-continued protrusion and eruption of igneous rocks along 
such lines of vent. 3dly. In local and partial eruptions and pro- 
trusions, producing valleys of elevation, local derangements, and other 
phsenomena that terminate in ordinary volcanic action. Elevatory 
forces, when considered in this general way, explain the phaenomena 
of strike — the parallelism of great contemporaneous elevations — as 
well as the exceptions to the rule of parallelism. 

GROUPS OP THK CUMBRIAN SECTION, &C. 

The author then commences the separation of the whole series of 
rocks of the second class into natural groups, founded on sections ex- 
hibited in the several districts above noticed ; and after shortly dis- 
cussing two sections connecting the Cheviot bills with the formations 
in the basin of the Tweed, he describes in some detail a transverse 
section through the whole system of the Cumbrian mountains, whieh 
exhibits the following groups in ascending order. 

(1.) The group of Skiddaw Forest, &c., the lower part of 
which rests on the granite, and passes into a system of crystalline 
strata resembling the rocks of the first class ; the upper part abounds 
in a fine dark glossy clay slate, interrupted here and there by beds 
of more mechanical structure. The whole is of great thickness, al- 
most without calcareous matter, and without any trace of organic 
remains, and forms the mineral axis of the Cumbrian mountains. 

(2.) A group essentially composed of quartzose and chloritic roof- 
ing slates alternating with mechanical beds of coarser structure, and 
also with innumerable igneousrocks (compact felspar,felspar porphyry, 
brecciated porphjnries, &c. &c.,) which partake of all the accidents 
of the slates. It is of enormous thickness, and rises into the highest 
mountains of the country ; and though chiefly developed on the 
south side of the preceding group (No. 1), it also appears extensively 
on the north side of the lower group, which thus forms a mineral axis 
«— a fact not yet noticed in any of the published geological maps. 



English Stratified Rocks inferior to the Old Red Sandstone. 303 

Though abounding in calcareous matter, it has no organic remains. 
{Lower Cambrian system). 

(3.) A great series, exjianded through Westmoreland and parts of 
Lancashire and Yorkshire. Itis based on calcareous slates, passing into 
limestone, and full of organic remains, and in its lower division are fine 
roofing slates, but less crystalline than those of the preceding group. 
Its upper division (not however separable by any very distinct zoologi- 
cal or mineralogical characters from the lower) abounds in arenaceous 
flagstone, coarse quartzose greywacke, coarse slates with imperfect 
cleavage, and not fit for use, and the series is incomijlete, being cut 
ofi^ by the unconformable deposits of old red sandstone and carboni- 
ferous limestone. Distinct beds of limestone are almost wanting in 
this upper division, and organic remains are very rare, but they ap- 
pear here and there in very thin bands among the coarse siliceous 
slates. Provisionally, the lower division is placed in the Upper 
Cambrian system, and the upper division in the Silurian system ; but 
without being separable into any further clear subdivisions. This 
great group (No. 3.) does not appear on the north side of the 
mineral axis of Cumberland, as was represented in the early geolo- 
gical maps. 

SECTIONS OF NORTH WALES, &C. 

The author next discusses a series of sections illustrating the 
structure of North Wales. One is drawn from the Menai Straits, 
in a direction about E.S.E., so as to cross theBerwyn chain and end 
in the carboniferous series near Oswestry. The others are drawn 
from the Berwyn chain to different parts of the carboniferous lime- 
stone range on the north side of Denbighshire. The greater por- 
tion of the first section crosses the older beds (the Cambrian System) 
which strike towards the N.E. The other sections intersect the 
upper series (Silurian System) which strike towards the N.W., 
passing (in some places unconformably) round the beds of the older 
system. From a consideration of the whole evidence the rocks are 
grouped in the ascending order as follows. 

(1.) Chlorite slate, quartz rock, and mica slate of Anglesea and 
Caernarvonshire. These are placed on the parallel of the first class ; 
and nothing is discovered in the section that is perfectly analogous 
with the Skiddaw slate, or first Cumbrian group, above described. 

(2.) The old slate series of Caernarvonshire and Merionethshire, 
alternating indefinitely with bands of porphyry and felspar rock; 
many parts absolutely identical in structure with the second Cum- 
brian group above-described. It is of enormous but unknown thick- 
ness, and is bent into great undulations, the anticlinal and synclinal 
lines of which are parallel to the strike of the chain. Through wide 
tracts of country it is without fossils ; but at Snowdon and Glider 
Fawr, encrinites, corals, and one or two species of bivalves have 
been discovered in it. It ends with the calcareous beds which range 
from Bala to the neighbourhood of Dinas Mowddy. This is called 
the Lower Cambrian System. 

(3.) The next group (the Upper Cambrian System) commences with 



304< Geological Society : Prof. Sedgwick on the 

tlie fossiliferous beds of Bala, includes all the higher portion of the 
Berwyns, and all the slate rocks of South Wales which are below 
the Silurian System. Its slate beds are less crystalline, and its 
general structure is more mechanical, than the preceding group, and 
it contains incomparably more fossils, which (though there are many 
extensive portions of the group without fossils) are disseminated 
through the more calcareous beds in great abundance. Many of the 
fossils are identical in species with those of the lower division of the 
Silurian System, nor have the true distinctive zoological characters 
of the group been well ascertained. 

In many parts of South Wales it is separated from the Silurian 
System by great faults and derangements of the strata, marked by a 
broad band of rotten non-fossUiferous schist. At the north end of 
the Berwyn chain it appears to pass by insensible gradations into the 
lower division of the Upper System (the Caradoc Sandstone). 

(4.) The last natural group (the Silurian System). For all details 
respecting this system the author refers to the abstracts of Mr. Mur- 
chison's papers*, and to his forthcoming work. He then describes the 
sections : 

(1.) East of the Berwyns, in which the Caradoc Sandstone is finely 
developed ; containing the Llandeilo flagstone and other character- 
istic calcareous and shelly bands. 

(2.) The sections north of the Berwyns, connecting Montgo- 
meryshire with Denbighshire. The ascending series is described as 
follows : — 

(1.) A series of beds several thousand feet in thickness, and ap- 
parently forming a passage between the Upper Cambrian and 
lowest portion of the Silurian System. 
(2.) Bands of calcareous slate with numerous organic remains of 

the " Caradoc Sandstone." 
(3.) Series of flagstones, more or less calcareous, with many or- 
thoceratites and two species of cardiola, overlaid by, and as- 
sociated with, irregular masses of roofing slate with a trans- 
verse cleavage. 
(4.) Flagstones and rotten slates, many parts in an imperfect 
state of induration, and the whole surmounted by the Car- 
boniferous Limestone. — Of the preceding section the lower 
part of No. 3. is identical with the series of Long Mountain 
in the Silurian sections of Mr, Murchison ; but No. 4. is 
mineralogically unlike [any thing he has described, although 
it has been found to contain some of the fossils of the Upper 
Ludlow Rock. It appears from these details that the Silurian 
System, although its subdivisions are obscure from the abs- 
ence of the Wenlock and Ludlow limestones, is more fully 
developed than in the group (No. 3.) of the great Cumbrian 
section above described. 
The author then briefly notices the slate rocks of Charnwood Fo- 
rest, which he refers provisionally to the Upper Cambrian System ; 

[* See Lond. and Edinb. Phil. Mag., vol. iii. p. 224 ; vol. iv. p. 159, 228, 
370, 450 J vol. v. p. 217 ; and vol. vi. p. 314, 37G.] 



English Stratified Rocks inferior to the Old Red Sandstone. 305 

but from the imperfection of the sections and the absence of organic 
remains, their exact place is not determined. 

SECTIOJf FROM THE NORTH TO THE SOUTH COAST OF DEVONSHIRE. 

I. North Devon section. — For details the author refers to a paper 
by Mr. Murchison and himself, but enumerates the successive 
groups for the purpose of adding some remarks, and of connecting 
the system of Devon with that of Cornwall*. The ascending order 
is as follows : 

(1.) A series of coarse arenaceous slates, not noticed in the for- 
mer paper. 
^2.) The calcareous slates of the river Lyn. 
(3.) The coarse red flagstones, &c., of Exmoor Forest, and of the 

coast to the east of Combe Martin. 
(4.^ The calcareous slates and limestone bands of Ilfracombe. 
^5.) The contorted slate zone south of Ilfracombe. 
^6.) The calcareous slates and irregular masses of limestone be- 
tween the preceding group and. the culm measures. 
The whole of the preceding series is placed in the Upper Cambrian 
System with the exception of the upper portion of No. 6., which is 
considered, both from its structure and its fossils, as near the doubt- 
ful limit between the Upper Cambrian and Lower Silurian Systems. 

II. Culm measures. — This series is described (as in a former paper) 
to occupy a great trough, which ranges across the country in a di- 
rection bearing nearly east and west ; on its north side overlying 
the preceding group (No. 6. of the North Devon section), and 
on its south side rising up to the granite of Dartmoor, or overlying 
the older slate system of Devonshire 'and Cornwallf. Its subdivi- 
sions are enumerated as in the former paper ; and the author adds, 
that during the summer of 1837 he ascertained that the lower beds 
of the culm measures rest unconformably on a portion of the slate 
rocks in the north of Cornwall, near Launceston. On the contrary, 
in the cliffs near Barnstaple, the lower culm measures seem to gra- 
duate almost insensibly into the formation on which it rests. Hence 
(independently of all other evidence) it is clear that the slate rocks in 
the north of Cornwall are of an older epoch than the upper group 
of the North Devon section. 

The author then considers the classification of the culm series, and 
states his opinion that the base of it is lower than the base of the 
ordinary English carboniferous series. The base line (in the former 
jiaper) was intentionally left in an ambiguous position ; and the dif- 
ficulty of the subject has been subsequently increased by the supposed 
discovery of some true carboniferous plants in the highest group 
(No. G.) of the North Devon section. In the upper part of the culm 
measures all the fossil plants have been described as identical in spe- 
cies with plants of the carboniferous series ; and hence (unless some 

* See Proceedings of Geological Society, vol. ii. p. 55G et seq, [or L. & 
E. Phil. Mag. vol. xi. p. 311.] 

t See Proceedings, vol. ii. p. 561. [L. & E. Phil. Mag. vol. xi. p. 315, 316.] 
Phil Mag. S. 3. Vol. 13. No. 82. Oct. 1838. X 



306 Geological Society : Prof. Sedgwick on the 

conflicting evidence be discovered) the culm measures and common 
coal measures must continue to be placed on the same parallel. 

Lastlj', he states that, independently of any question of classifica- 
tion, the former paper by Mr. Murchison and himself first pointed 
out the following facts in the general structure of the county : — 

(1.) That the Wavellite rock and culm limestone (of Barnstaple, 
&c.) were in position, structure, and fossils distinct from all the other 
calcareous groups of Devon. 

(2.) That the same group was repeated over again with a reversed 
dip on the north side of Dartmoor, and entirely distinct from the calca- 
reous slates of Cornwall, with which it had no analogy in structure 
or fossils. 

(3.) That the Holcombe Rogus limestone was a part of the culm 
series. 

(4.) That the culmiferous system was superior to all the slate rocks 
of Devonshire and Cornwall, and was overlaid by no older rock than 
the new red sandstone. Whereas before, the portion of the culm 
series near the granite had, from its metamorphic structure, been 
confounded with the oldest rocks of Devonshire and Cornwall ; and 
the position of whole series among the Devonian groups had been 
misapprehended. 

III. South Devon section. — This section, in conformity with the 
scheme given in the former paper, is as follows, in the ascending 
order* : — 

(1.) A series of slate rocks subdivided into two groups, — the lowei 
containing a few calcareous bands, the upper group more calcareous 
and ending with the Plymouth limestone. The two are considered 
as one formation ; and the name, Ashburton bands, which had been 
given to the calcareous beds of the lower division, is now withdrawn, 
as the position of the Ashburton lime rock is considered ambiguous. 
The name of Ugborough bands is not liable to the same objection. 

(2.) A great group of coarse red flagstone and slate, identical in its 
structure with No. 3. of the North Devon section, and containing 
some corals that do not appear in the mountain limestone, but are 
found both in the Cambrian and Silurian systems. This group is 
provisionally identified with No. 3, of the North Devon section. 

(3.) A great group of slate rocks without beds of limestone, and 
very rarely with any traces of organic remains. By the suppression 
of No. 4., this group is considered as the equivalent of No. 5. of 
the North Devon section. 

(4.) Mica and chlorite slate, anomalous in structure and position, 
and forming no part of the ascending series. 

The preceding identifications are only provisional, and many desi- 
derata are enumerated ; but it is considered certain that the South 
Devon section belongs, on the whole, to a lower series than the 
North Devon. Neither of them are, however, supposed to descend 
lower than the Upper Cambrian, or the higher part of the Lower 
Cambrian, group. To place the South Devon section above the North 

* See Proceedings, vol. ii. p. 5G2. [or L. & E. Phil. Mag. vol. xi. p. 
310,317.] 



English Stratified Rocks inferior to the Old Red Sandstone, 307 

Devon, would be to violate all the analogies of structure derived from 
other parts of England ; and would not, the author believes, be sup- 
ported by any specific evidence derived from fossils. 

CLASSIFICATION OF THE KOCKS OF CORNWALL. 

The author states, that the Plymouth limestone, in its range west- 
wards, gradually thins off, and comes to an edge about the middle 
of Whitesand bay. The strike of the beds and the trending of the 
coast prevent this limestone and all the upper groups of the South 
Devon section from appearing again on the south-eastern side of 
Cornwall. 

The inferior portion of the first group (No. 1.) of the South Devon 
section passes into Cornwall in a broad zone, gradually acquires the 
strike of the Cornish rocks, and so runs along the S.E. coast; and 
finallj'^ passes from Falmovith bay to Mounts bay ; rising on its north 
side towards the granite, and on its south side dipping under the ser- 
pentine of the Lizard district. As in Devonshire, the group contains 
beds more or less calcareous, and, rarely, thin beds of limestone. 

In the same way, though not with the same clear evidence, the 
calcareous slates rising from beneath the culm-measures near Laun- 
ceston, double round the granitic promontory of Rough-Tor, and 
are thence expanded (though with considerable irregularities of 
strike and modifications of structure) as far as St. Ives' Bay, 

The granitic ridge of the county is supposed to represent an in- 
terrupted mineral axis, on the N.E. and S.W. sides of which are 
slaty groups of the same geological period. In all cases near the 
granite the slaty groups change their structure ; but this change of 
structure cannot be assumed as the ground of a classification depend- 
ent on the age of the deposit ; as it is shown by a series of sections, 
that in several places the fossiliferous slates on the coast are of the 
same date with the indurated metalliferous slates that rise to the 
granite. Hence the crystalline and metalliferous slates of Cornwall 
are considered as metamorphic, and in that respect agree with the 
bottom culm series that touches on the Dartmoor granite. 

Of the rocks of Cornwall the newest are the granites ; next come 
the serpentine and other trappean rocks ; and the oldest are the slate 
rocks. These slate rocks (including all the killas of Cornwall of 
whatever structure) appear to be an actual prolongation of the lowest 
group of the South Devon section, and therefore, agreeably to what 
is stated above, are provisionally arranged near the upper portion of 
the Lower Cambrian System. 

Many of these rocks were formerly considered primitive ; but none of 
them have any pretension to that class. Numerous fossils were found 
by the author in the cliffs on both sides Loe bay, and on both sides 
of the Fowey river, and still further west in Gerrans bay. The Rev. 
J. J. Conybeare found fossils many years since in the Tintagel slates ; 
and the author in 1828 traced the fossiliferous system into the cliffs 
west of Padstow. During M. De la Beche's survey he had (before 
the author's last visit to the N.W. coast of Cornwall) found fossils 
innumerable in that part of the county. The Cornish fossils are 

X2 



308 Geological Society : Prof. Setlgwick on the 

generally ill preserved ; but among them are some corals that are 
common both to the Silurian and Cambrian systems. The fossils of 
New Quay and South Petherwin are an exception to the remark ; as 
many of them are well preserved. They consist of corals ; encri- 
nites ; numerous specimens of the genera Terehratula, Orthis, and Spi- 
rifer; of four or five species of OrfAocer«ii7es; Goniatites; and lastly, 
three or four new species of a genus described by Count Munster 
under the name Clymene, and by Mr. Ansted under the name En- 
dosiphonites. As they occupy a position so much lower, so, as a 
group, these fossils are distinct from those of the Silurian system. 

Conclusion. — The author here takes a retrospect of the preceding 
description, and states that the classifications are founded on the 
details of actual sections ; and that as far as such detailed sections 
throw light on the several questions that may arise, there is not 
much that remains to be done in England. Some of the generali- 
zations are, however, founded on imperfect evidence ; and to render 
them more complete, it is now necessary to appeal to the organic 
remains in the several groups. In this department little has been 
yet effected, excepting in the higher part of the Silurian system, 
where the upper divisions (at least in one part of the island) assume 
definite mineralogical and zoological types. Whether definite zoolo-^ 
gical groups can be made out in any lower system still remains to 
be seen. The rigid determination of the Devon and Cornish fossils, 
which are very numerous, and a rigid comparison of the Berwyn and 
Bala fossils with those near the base of the third group of the Cum- 
brian section, give the fairest promise of an answer to the question, 
and are pointed out as immediate desiderata. 

The difficulty of classification by organic remains increases as we 
descend, and is at length insurmountable ; for in the lowest strati- 
fied groups, independently of metamorphic structure, all traces of 
fossils gradually vanish; and the great range of certain species 
through numerous successive groups, and the very irregular distri- 
bution of fossils even in some of the more fossiliferous divisions, add 
greatly to the difficulties of establishing true definite groups even 
within the limits of our island. The difficulties are indefinitely 
increased in comparing the formations of remote continents. But 
these circumstances are compensated by the magnificent scale of de- 
velopment of the successive groups, and their wide geographical 
distribution. Taken together they have a great unity of character ; 
and even in remote continents they seem to form a common base, 
from which we may hope to compute the whole series of secondary 
and tertiary deposits that surmount them. 

The author then briefly touches on questions of structure and 
cleavage ; on the indefinite alternations of trappean beds ; on meta- 
morphic structure ; on the long duration of the deposits ; and on their 
great disruptions and symmetrical dislocations, indicating a greater 
violence of disturbing forces than is indicated in the secondary for- 
mations of this country. Following the geological scale of deposits 
from top to bottom, we can trace a series of phsenomena indicating 
the same kind of causation differing at different times in intensity 



English Stratified Rocks inferior to the Old Red Sandstone. 309 

and degree. The mean intensity can therefore only be collected 
by ascertaining the intensity during every geological period, and can 
never be obtained by assuming the intensity of any one e^joch, jjast 
or present, as the arbitrary standard. Again, the successive organic 
types indicate great physical changes ; and following the descending 
scale they at length vanish ; conducting us, however, to the confines 
of other investigations in exact science which must prove the ulti- 
mate basis of physical geology. 

Finally, the author gives a tabular arrangement of the several 
classes and subdivisions agreeably to the system of the preceding 
communication. 

Class I. — Primary stratified Groups. 
Gneiss, mica slate, &c., &c. Highlands of Scotland and the 
Hebrides. Crystalline slates of Anglesea and the S.W. coast 
of Carnarvonshire. 
The series generally without organic remains; but should organic 
remains appear unequivocally in any parts of this class, they may be 
described as the Protozoic system. 

Class l.(«.) The crystedline slates of central Skiddaw forest, and 
the upper Skiddaw slate series. The whole is inorganic and inter- 
mediate between Class I. and Class II. 

Class II., or Paleozoic series. 
This class Includes all the groups of formations between Class I. 
and the old red sandstone ; and is subdivided as follows : — 

1. Lower Cambrian System. — All the Welsh series under the Bala 

limestone. The two great groups of green roofing slate and 
porphyry on the north and south side of the mineral axis 
of the Cumbrian mountains. A small part of the slates of 
Cornwall and South Devon. ? A part of the slate series of 
the Isle of Man, &c., &c. 

2. Upper Cambrian Sy stein. — A large part of the Lammermuir 

chain on the south frontier of Scotland. A part of the third 
Cumbrian group, commencing with the calcareous slates of 
Coniston and Windermere. The system of the Berwyns and 
South Wales. The slates of Charnwood forest. } All the 
North Devon and a part of the South Devon series. The 
greater part of the Cornish series. 

3. The Silurian Systejn. — The upper part of the third Cumbrian 

group, chiefly expanded in Westmoreland and Yorkshire. The 

flagstone series of Denbighshire. The hills on both sides 

of Llangollen. The region east of the Berwyn chain. The 

regions described in the papers of Mr, Murchison, from which 

the types of the system are derived. The lowest part of the 

culmiferous series. ? 

Over all the preceding comes the Old Red Sandstone — divided into 

three great natural gromps in the country bordering the Silurian 

types of Mr. Murchison ; in the northern counties developed in a 

less distinct manner, chiefly in the form of great unconformable 

masses of conglomerate, appearing at irregular intervals between the 

preceding groups and the carboniferous series. 



310 Intelligence and Miscellaneous Articles. 

Little notice is taken in the memoir of the crystalline unstratified 
rocks associated with the several series. Any questions of classifi- 
cation, bearing on their geological epoch, can only be determined by 
the effects, produced by them on the stratified series, which mark the 
period of their first protrusion ; but for the present this subject is 
not touched on by the author. 

XLI. Ijitelligence and Miscellaneous Articles. 

CONTINUATION OF THE SCIENTIFIC MEMOIRS. 

"lylT'E are glad to be enabled to announce that sufficient sup- 
^^ port has been proffered by private individuals and 
public bodies, to secure the continuation of the Scientific 
Memoirs; and that the Fifth Part, being the commence- 
ment of a Second Volume, is in the course of preparation. 



SYNAPTASIN. 

M. Robiquet has given the name of synaptase to the principle of 
almonds, which possesses the singular property of reacting on amyg- 
dalin, and of determining, under the influence of moisture, the 
production of the oil of bitter almonds. The name of synaptasin is 
derived from the power of reuniting, as a connecting link, amygdalin 
and water. This substance possesses the following properties : it is 
of ayellowish white colour, sometimes brittle, and possessing the ap- 
pearance of a varnish like dried gluten ; at other times it is opake and 
spongy, like sarcocol. It is very soluble in cold water, but nearly 
insoluble in alcohol ; when heated to about 140° Fahr. it is coagu- 
lated, when in solution in water ; it is not precipitated either by acids 
or by acetate of lead, but readily by tannin; it does not like diastase 
form a paste when heated in water to 140° Fahr ; upon amygdalin 
it acts strongly, even at 176° Fahr.; when the solution is heated in 
contact with the air, it readily suffers a very evident decomposition, 
it becomes every day more turbid, and acquires a fetid smell, and, 
after a time, a very abundant flocky precipitate is formed ; when 
subjected to the action of heat, it tumefies, yields empyreumatic oil, 
and an acid which contains a little ammonia. This acidity induced 
M. Robiquet to suppose that it retained a little of the acetic acid 
used in preparing it ; when, however, it is put into contact with con- 
centrated sulphuric acid, it undergoes a kind of softening, but neither 
acetic nor sulphurous acid is disengaged ; when a drop of tincture 
of iodine is added to a solution of synaptasin, a deep rose-red colour 
is produced, but without any precipitation. 

Synaptasin is obtained by the following process : almonds which 
have been dei^rived of their oil by jDressure, are to be mixed with 
twice their weight of pure water, and the mixture is to be gradual- 
ly pressed. After two hours' maceration, the liquid is to be filtered, 
the albumen is precipitated by acetic acid, and after filtration the 
gum is to be separated by means of acetate of lead, and after again 
filtering, the excess of acetate of lead is to be separated quickly by 
hydrosulphuric acid, and the excess of hydrosulphuric acid is to be 



Intelligence and Miscellaneous Articles. 



311 



got rid of by the air pump ; the sulphuret is to be separated by the 
filter, and the synaptasin is to be precipitated by a sufficient quan- 
tity of alcohol. The sugar remains in solution, and the synaptasin 
after washing with alcohol is to be dried in vacuo. 

Journal de Chimie Medicale. — July, 1838. 



COMPOSITION OF THE BLOOD. 

M. Lecanu states that the venous blood of man may be considered 
on an average as composed of 

Serum 869-1547 

Globules 130-8453 



Or of 



1000- 

Water 790-3707 

Oxygen ' 

Azote 

Carbonic Acid 

Extractive matters 

Phosphorised Fat 

Cholestrine 

Serolin 

Free Oleic Acid 

Free Margaric Acid 

Hydrochlorate of Soda 

Hydrochlorate of Potash 

Hydrochlorate of Ammonia .... )> 10-9800 

Carbonate of Soda 

Carbonate of Lime 

Carbonate of Magnesia 

Phosphate of Soda 

Phosphate of Lime 

Phosphate of Magnesia 

Sulphate of Potash, 

Lactate of Soda 

Salt of fixed fat Acid 

Salts of volatile fat Acid 

Yellow colouring matter 

Albumen of the Serum 67-8040 

Globules 130-8453 



1000- 
The Globules are stated to be composed of 

Fibrin 2-9480 

Hematosin 2-2700 

Albumen 125-6273 



130-8453 
An, de Chimie, 67-64. 



313 Intelligence and Miscellaneous Articles, 

ON THE IODIDE OF AMIDIN. BY M. J. L. LASSAIGNE. 

In 1 833 the name of iodide of amidin was given by M. Lassaigne 
to the compound of iodine and the internal and soluble portion of 
fecula ; the properties of this singular compound were then stated, 
and the decolorating power of heat was mentioned. 

The results obtained by M, Lassaigne induced him to believe that 
this compound of iodine and amidin was soluble in water, contrary 
to the opinion of some chemists, who, subsequently to his experi- 
ments, endeavoured to show that this blue compound is merely sus- 
pended in the liquid in a state of extreme division. The observa- 
tions made by M. Lassaigne are confirmed by those which he has 
since made : 

1st. A solution of iodide of amidin prepared in July 1833, by 
pouring a solution of iodine into the soluble portion of fecula, ob- 
tained by treating the bruised grains with cold water, was placed in 
a dark closet. This solution, examined monthly to the present 
time during four years, has not yielded any deposit ; it has always 
had the appearance of an homogeneous solution, equally coloured 
throughout of a fine indigo blue ; and it has always had the aj^pear- 
ance of freshly prepared iodide of amidin. The long time which 
this solution has been kept, without any sensible diminution of in- 
tensity, proves that it exhibits all the properties of a true combina- 
tion ; for a simple solution of amidin in water underwent a complete 
decomposition in some weeks, or at any rate it lost the property 
of colouring a solution of iodine blue. 

2nd. The action of cold upon the above-described solution of io- 
dide of amidin corroborates the opinion which has been expressed 
of its nature. It was exposed in the winter to a temperature of about 
8° Fahr. ; it solidified and became of a black-blue. During one night 
in January in which the temperature was about 10° Fahr., it was 
exposed to the air, and became a solid mass, of a brownish yellow 
colour, which it lost as the temperature became higher, and returned 
to a deep blue ; placed in a warm room, it gradually liquefied, and 
during this change the iodide of amidin was deposited in flocks at 
the bottom of the bottle, the water remaining colourless. 

This coagulation of the iodide of amidin by the action of cold, and 
its separation from the water which held it in solution before conge- 
lation, is attributed by M. Lassaigne to the cohesion of its molecules, 
which modified its affinity for water; by heating this fluid, in 
which the iodine was suspended and not dissolved, to about 60° Fahr., 
it re-dissolved and formed a fine blue coloured solution, and possess- 
ed all the characters which it had before congelation. 

This observation, added to the former, leaves no doubt that iodide 
of amidin is really soluble in water at common temj)eratures, and 
that it evidently separates when a physical cause produces the ap- 
proach of its molecules, or a chemical action determines its union 
with other bodies, which then render it insoluble in water. 

It was found that a freshly prepared solution of iodine did not as- 
sume the brownish yellow colour, which the long prepared solution 
did when exposed to a low temperature. This difference is attri- 



Intelligence and Miscellaneous Articles. 313 

butecl by M. Lassaigne to some change which had probably occurred 
in the nature of the long-kept solution. 

Journal de Chimie Medicate. — May, 1838. 



NEW COMPOUND OF SULPHATE OF MAGNESIA AND WATER. 

M. Fritzche states that when a concentrated solution of sul])hate 
of magnesia is exposed to the temperature of freezing water, there 
soon form, in the midst of small lamellar crystals of ice, a salt 
white as enamel and in smaller or larger crystals, according as the 
quantity of the solution is small or great. "When large masses of this 
solution are allowed to cool during the winter, the salt often se- 
parates in crystals of a finger's length, and by gently thawing the 
liquid, they may be separated, for they undergo no change in water 
at 32°. 

The enamel- white appearance which these ciystals exhibit, arises 
from their consisting of a great number of still smaller crystals ; the 
distinct crystals obtained by this process on the large scale have not 
the enamel tint, but are limpid and transparent. When subjected 
to a temperature above 32°, this compound soon begins to decom- 
pose ; water separates ; the crystals become opake, and common 
sulphate is obtained with seven atoms of water. The new crystals 
retain their form, but the interior contains small crystals of the 
common sulphate. These crystals could not be dried even between 
folds of blotting paper without losing some water, and become 
slightly opake at the surface : submitted to analysis the crystals 
were found to consist very nearly of 

One eq. of sulphate of magnesia 60 = 35" 7 7 

Twelve eqs. of water 108 = 64-23 



168 100- 
L'Institut, Fev. 1838. 



ON CHLORETHERAL BY M. FELIX d' ARCET. 

When rough chloride of hydrocarbon is distilled in a water bath 
at 122°, there is readily obtained a liquor which boils at 185° Fahr., 
and this is pure chloride of hydrocarbon ; the distillation then soon 
stops, and there remains in the retort a liquid of an oily a])pearance, 
which does not begin to boil until heated to about 284° Fahr., and 
its boiling point rises to 324°, and then remains stationary. 

This liquid is about one fourth or one fifth of the original product, 
according as the washing-bottles of the olefiant gas have been cooled 
with greater or less care. 

Several experiments yielded the same results, and they were per- 
fectly identical. 

When freed from all extraneous matter, this substance is an ex- 
tremely fluid liquid, colourless, limpid, and free from the smell of 
chloride of hydrocarbon. It has however a peculiar sweetish, aethereal 
odour, resembling that of sweet oil of wine ; it bums, when a taper 
is presented to it, with a green flame. 



314 Intelligence and Miscellaneous Articles. 

The density of its vapour is 4'930 ; and by analysis it yielded 

Hydrogen 5"41 

Carbon 34*45 

Oxygen lO'SO 

Chlorine 49'34— 100' 

The formula according to M. D'Arcet is H** C** O C1-. 

Calculated. 

H8 50 5-5 

C8 306 34-7 

O 100 105 

CP 442 49-3 



898 100- 

Excess of chlorine does not act upon this substance, or at any 
rate no new compound arises from their contact ; this is also the 
case with ammonia. 

This body appears to be, according to M. D'Arcet's nomenclature, 
the chloral of aether ; except that, according to the law of substitu- 
tions, as the hydrogen which has disappeared, and which is replaced 
by chlorine, must belong to the water which constitutes the hydrate 
of the carburetted hydrogen of the aether, it ought not to be replaced. 
Do not the following formulae, inquires M. D'Arcet, appear to ex- 
plain the reaction } 

C« H8 + H2 O = C8 H«o O sulphuric aether. 
CsH'oQ 

H2 C2 C2 



C8 H8 C2 O chloretheral. 

Annates de Chim. et de Phys., [xvi. 108. 
[What is called the law of substitutions, about which no small pa- 
rade is made by some foreign chemists, when stripj^ed of its name 
means merely, I believe, what has been known ever since the doctrine 
of definite proportions was first established by Dr. Dalton, that when 
a definite quantity of any substance is displaced, that which re- 
places it is equally definite. I am not sure that I have rightly 
understood the author, and shall give a part of his statement in the 
original French : " Ce corps parait etre le chloral de I'ether ; seule- 
ment, d'apres la loi des substitutions, comme I'hydrogene qui a dis- 
l^aru, et qui a etc remplace par du chlore, doit appartenir a I'eau qui 
constitue I'liydrate d'hydrog^ne carbone de I'ether, il ne devait pas 
etre remplace." 

The simplest view of the nature of this fluid is perhaps to consider 
it as an oxichloride of hydrocarbon, composed, according to the equi- 
valents usually adopted in England, of. 

Four eqs. of hydrogen 4 or 5*5 

Four eqs. of carbon 24 or 33"4 

One eq. of oxygen 8 or 11*1 

One eq. of chlorine 36 or 50* 

72 100- 

[R. P.] 



Intelligence and Miscellaneous Articles. 315 

FORMIO-BENZOILIC ACID. 

M. Laurent states when Nordhausen sulphuric acid is made to act 
upon the oil of bitter almonds, (hydruret of benzule,) they combine 
with the extrication of heat, and solidify into a fibrous mass. If 
water be poured upon it, two strnta are formed, the lower one of 
which is acid, and the upper one oily. The oily stratum, which gra- 
dually solidifies, is a constant compound of 2 Bz + f H^ O ; but it 
may present itself under two different and incompatible forms. 

The liquid constituting the lower stratum, according to M. Lau- 
rent, is the formio-benzoilic acid. He says that it is formed at the 
expense of the hydrocyanic acid, which is decomposed by the influ- 
ence of water and sulphuric acid, and gives rise to sulphate of am- 
monia and formic acid, which, being in the nascent state, combines 
with the hydruret of benzule to form the formio-benzoilic acid. — 
Journal de Chimie Medicate, November 1837. 



PROPORTIONS OF GLUTEN IN GRAIN. 

M. Boussingault has made researches on the proportions of gluten 
contained in the flour of different kinds of grain cultivated in the 
same soil. 

He determined the quantity of gluten by ascertaining that of the 
ammonia which each yielded ; this plan, it will be readily conceived, 
will yield much more precise results than that of working the flour 
between the fingers under a stream of water. 

The flour obtained from diiFerent kinds of corn, but cultivated in 
the same soil, (that of the Jardin des Plantes,) yielded diff'erent pro- 
portions of gluten in the proportion of 15 to 21. The diff^erences 
dependent upon the influence of the soil and that of the climate are 
much more strongly marked, and M. Boussingault has observed them 
to amount to from 1 to 4. — Journal de Chimie MMicale, November 
1837. 

OXIDE OF PHOSPHORUS. 

M. Le Verrier proposes the following method of obtaining pure 
oxide of phosphorus, which he is of opinion has not been previously 
procured : take a glass globe, capable of holding about 2 pints, the 
neck of which is about 4 inches long and one inch wide ; pour into 
this a little chloride of phosphorus, then introduce of phosphorus, 
previously dried on paper, and cut into pieces of about 8 grains each, 
enough to form a stratum of four-fifths of an inch thick, at the bot- 
tom of the globe : then add sufficient chloride of phosphorus to co- 
ver the phosphorus, and expose the whole to the air; 8 or 10 globes 
thus prepared are required to obtain 30 grains of oxide readily. 

When about 24 hours have elapsed, a thick white crust of phos- 
phatic acid is formed at the surface of the solution, whilst below the 
stratum of phosphorus there may be seen, through the glass, a yel- 
low substance attached to it at the bottom of the globe ; this is a 
compound of phosphoric acid and oxide of phosphorus, which the 
author calls phosphate of oxide of phosphorus. 

In 24 hours after the appearance of the whitish matter, the quan- 



316 Intelligence and MiscellUneous Articles, 

tity of phosphate appears, in general, to be at its maximum. The 
chloride of phosphorus must then be poured off to make it serve for 
a fresh operation ; the pieces of phosphorus which adhere together, 
at the bottom of the globe, must be detached, and gradually allowed 
to fall into cold water. By this proceeding, the considerable increase 
of temperature is avoided, which would otherwise occur, by a too 
rapid solution of the phosphoric acid, and of the excess of chloride 
of phosphorus ; this would occasion the decomposition of the phos- 
phate of oxide, as will presently appear. I'he water soon becomes 
of a deep yellow colour by dissolving the phosphate of oxide ; and 
by decanting and filtering to free it from the suspended phosphorus, 
a perfectly limpid yellow liquid is obtained. By heating this solu- 
tion, the phosphate of oxide decomposes at about 177° Fahrenheit 
into phosphoric acid, and a yellow, finely-divided, flocculent matter, 
which, however, collects pretty rapidly at the bottom of the water. 
This substance is hydrated phosphoric oxide, which is nearly inso- 
luble in water. This hydrate may, in a short time, be washed upon 
a filter with hot water ; but in order to have the product not soiled 
by the paper, it must not be dried upon the filter, but it must be 
removed from it, while moist, to a porcelain capsule, and dried, in 
vacuo, over sulphuric acid. The oxide not only loses the interposed 
water, but also that which it contained in combination : the hydrate 
is decomposed, and perfectly pure oxide of phosphorus remains ; it 
has the form of small grains, which are of a red colour ; but when 
finely powdered, it is canary yellow. 

It was proved to contain no chlorine, by dissolving in nitric acid, 
and finding none in the solution, and it contained no hydrogen ; for 
by burning with oxide of copper, it yielded no water. By converting 
this oxide into phosphoric acid, and that into phosphate of lead, it 
was found to consist, very nearly, of 

Oxygen 11-35 or 1 eq. 8 

Phosphorus .... 88-65 or 4 eqs. 64 



100- 72 

This oxide is insoluble in water, alcohol and aether ; its density is 
greater than that of water. At the moment of withdrawing it from 
the vacuum, it has neither smell nor taste, and it remains in this 
state, either in contact with the air or dry oxygen. But when these 
gases are moist, it slowly acidifies, yielding a slight odour of phos- 
phuretted hydrogen. It is not luminous in the dark under any cir- 
cumstances. 

Out of contact with the air it may be kept at a temperature of 
about 570° without decomposing, but it becomes of a bright red 
colour ; at a little below the heat of boiling mercury, it decomposes 
rapidly, phosphorus distils, and perfectly white phosphoric acid re- 
mains. When heated in the air, it remains unchanged at a high 
temperature, and it burns only when it disengages phosphorus. 
Chlorine converts it into chloride of phosphorus and phosphoric acid. 
Hydrochloric acid, whether gaseous or in solution, has no effect 
on this oxide ; when heated with concentrated sulphuric acid, sul- 



Intelligence and MIscellaneons Articles. 317 

phurous acid is given out ; nitric acid converts it into phosphoric 
acid. 

When mixed w^ith chlorate of potash it gives a fulminating pow- 
der, which detonates, sometimes, during the mixture, and without 
giving it any pressure ; a slight pressure always occasions it to ex- 
l)lode. The hydrate of phosphorus, which has been mentioned, de- 
composes in vacuo, or by exposure to the air at common temperatures. 
The quantity of water which it contains was determined by indirect 
processes to be 20*5 per cent., so that it is composed of one eq. of 
oxide 72 + 2 eqs., water 18 = 90, very nearly. — Annates de Chimie 
et de PJiysique, Juillet 1837. 



BORATES OF POTASH. BY M. LAURENT. 

The borates of potash were prepared by decomposing a hot solu- 
tion of carbonate of potash with excess of boracic acid. A part of 
the salt was made to crystallize, and to the remaining solution a 
little caustic potash was added, and crystallization was effected after 
each addition of the alkali. The crystals which were formed were 
kept separate and examined. 

Sexbonite of Potasli is deposited from a solution which is either 
acid or neutral to litmus paper. The crystals belong to the right 
prismatic system (right rhombic prisms) and are generally modified 
on the edges or angles, and are occasionally tabular and thin. The 
forms are not readily perceived on account of the crystals being 
hemitrope. 

This salt is unalterable in the air ; very brilliant ; it is but slightly 
soluble in cold water, but readily dissolved by boiling water; it is 
neutral to litmus paper, or rather it blues it slightly. 

This salt was analyzed by passing gaseous hydrofluoric acid on 
the pulverized borate, moistened and placed in a platina crucible ; 
the fluoride of potassium was converted into neutral sulphate by 
sulphuric acid, calcination, and the addition of carbonate of ammonia. 
The results of the analysis were — 

By Experiment. Calculated. 

Boracic Acid - - - 60-8 60-5 

Potash 14-0 1.3-6 

Water ----- 25-2 25-2 



100-0 

The calculation was made according to the following formula : — 
6B^03 + K O 4 10H"-O. 

Taking Berzelius's recent atomic weight of boracic acid as B'^ O^, 
it will be seen that this salt, which is rather alkaline than acid, con- 
tains, nevertheless, six atoms of acid. 

Triborate of Soda. On gradually adding potash to the preceding 
salt, the liquor becomes alkaline, and by evaporation it deposits at 
first a confusedly crystalline crust, which appeared, however, to be 
sexborate, and the mother waters eventually yielded biborate. Some- 
times, and especially at the surface of the solution, there are 
formed very distinct crystals presenting the form of rectangular 



318 Intelligence and Miscellaneous Articles. 

prisms, the terminal edges being replaced by planes that produce 

four-sided pyramids on each base. 

This salt consists of — By Experiment. Calculated. 

Boracic Acid - - - 46*4 47 

Potash 21-G 21-0 

Water 32-0 320 



100-0 100-0 

The formula is 3 B"- Qs + K O + 8 H« O. 

These crystals are unalterable in the air, and, like the preceding, 
they fuse readily, and swell but little. 

Rhombic Biborate of Potash. This salt, the composition of which 
corresponds to that of octahedral borate of soda, possesses, neverthe- 
less, a different and an incompatible form ; it generally crystallizes 
in hexagonal prisms, and rarely as an acute rhomboid — primary 
form, an acute rhomboid occasionally with the lateral angles re- 
placed, or as a bipyramidal dodecahedron or hexagonal prism. 

This salt is alkaline, very soluble in cold and in boiling water ; 
when fused it swells up like borax ; it is composed of — 

By Experiment. Calculated. 

Boracic Acid ... 43-7 43-2 

Potash 28-5 29-5 

Water 27-8 27-8 

100-0 1000* 

The formula is 2 B'^ 0^ + K + 5 H^ O, 

Sexborate of potash does not precipitate magnesia, oxide of man- 
ganese or oxide of silver, from solution ; the following are the effects 
which it produces in the annexed metallic solutions : — 

Barium "| A white precipitate, which disappears on the 
Strontium > addition of excess of water ; the solution 
Calcium J becoming slightly alkaline. 
Peroxide of iron, a rusty yellow precipitate. 
Copper, bright blue ditto. 

Nickel, greenish. 

Chromium, green. 

Lead, white. 

Silver, white, which disappears on the addi- 

tion of excess of water. 

An. de Ch. et de Ph. 67—215. 



CYANIDE OF GOLD. 

M. Deferre prepares this compound by dissolving IG parts of 
gold, cut into small pieces, in 80 parts of aqua regia, heated in a 
sand-bath ; to the solution there are to be added 24 parts of cya- 
nide of mercury, dissolved in 24 parts of distilled water ; the whole 
is to be evaporated to dryness, and the residue treated with 192 

* There is a mistake here in the original ; the substances amount to 
100-5. 



Meteorological Observations, 319 

parts of distilled water ; agitate the mixture, allow it to remain for 
some time, and then pour off tlie liquor from the cyanide of gold. 

To the mother water add 8 parts of cyanide of mercury, and 
again evaporate to drj'ness , again add 192 parts of distilled water 
to the dry residue, and again agitate ; suffer to remain, and pour off 
from the cyanide of gold ; this may he repeated a third and a fourth 
time, or until no more cyanide of gold of a fine colour is produced ; 
the operation with the mother water may be repeated without its 
being necessary to add cyanide of mercury every time. 

All the cyanide of gold obtained ought to be afterwards washed 
with distilled water, till it comes away quite insipid, or until re- 
agents show that it is entirely free from bichloride of mercury. 

Every time the mother water is used, it should be slightly acidi- 
fied with a few drops of aqua regia ; without this the cyanide of 
gold which separates would acquire by evaporation a yellow red- 
dish colour. During the evaporation to dryness on the sand-bath, 
the solution should be constantly stirred with a glass rod, till it ac- 
quires a bright canary yellow colour ; the occurrence of this denotes 
the formation of the cyanide of gold, mixed with bichloride of mer- 
cury, and an excess of cyanide of mercury undecomposed ; these are 
got rid of by washing with distilled water. 

The new Codex recommends the employment of pure cyanide of 
potassium as being essential to the success of the operation ; but the 
difficulty of procuring this salt in a pure state is well known. Be- 
sides, the instability of this salt, even when it is kept in well- stopped 
bottles, will always throw uncertainty on the results of the opera- 
tion ; an objection which does not attach to the use of cyanide of 
mercury. — Journal de Pharmacie, xxiv. p. 27. 



METEdROLOGICAL OBSERVATIONS FOR AUGUST 18.S8. 

Chisivick. — August 1. Very fine : heavy rain at night. 2. Rain. 3. Fine. 4, 
Overcast : slight rain. 5. Cloudy. 6. Sultry, with showers. 7. Showery. 
8, 9. Fine. 10. Overcast. 11 — 16. Very fine. 17. Hazy : slight rain. 18 — 20. 
Very fine. 21. Showery. 22. Rain. 23. Showery. 24, Cloudy and fine. 
25. Foggy : rain. 26, 27. Very fine. 28. Overcast : lightning at night. 
29. Cloudy and fine. 30. Clear and dry. 31. Very fine. 

Boston. — August 1. Fine. 2. Cloudy: rain early a.m. 3. Rain. 4. Fine: 
rain p.m. 5. Fine. 6. Cloudy : rain p.m. 7. Heavy rain with thunder and 
lightning P.M. 8. Cloudy. 9. Fine ; rain p.m. 10. Cloudy : rain p.m. 11,12. 
Cloudy. 13—15. Fine. 16. Cloudy. 17,18. Fine. 19,20. Windy. 21. 
"Windy : rain early a.m. : rain p.m. 22. Windy : rain p.m. 23. Stormy. 
24, 25. Fine. 26. Cloudy. 27. Cloudy : therm. 74° 6 p.m. 28. Cloudy. 
29. Windy: rain early a.m. 30,31. Fine. 

Jipplegarlh Manse, Dunifrks-sldre. — August 1. Rain p.m. : warm and moist. 
2. Fine day throughout. 3. Fine day : occasional showers. 4. Moist and 
cloudy. 5. Heavy rain p.m. 6. Very heavy showers. 7- Showery all day. 
8. Fine summer day : cool p.m. 9. Wet throughout. 10. Fair a.m. : wet 
evening. 11. Drizzling rain a.m.: fair p.m. 12. Fair: shower p.m. 13. 
Fair: shower at noon. 14. Fair throughout. 15. Fine clear day. 16. Tem- 
perate: cool. 17. Beautiful summer day. 18. Cloudy: moist p.m. 19,20. 
Showery all day. 21. Rainy all day : flood. 22. Showery all day. 2,3, 24. 
Fair a.m. : shower p.m. 25. Very moist : rain p.m. 26. Fair : warm : cloudy. 
27. Fair, but tlireatening. 28. Drizzling all day. 29. Clear and cool. 30. 
Temperate. 31. Mild though cloudy. 



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THE 

LONDON AND EDINBURGH 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



NOVEMBER 1838. 



XLII. On a Principle laid down by Clairaiitybr determining 
the Figure of Equilibrium of a Fluids the Particles of 'which 
are urged by accelerating forces. (Theorie dela Figure dela 
Terre, premiere partie, chap. 5'"^) ^j/ James Ivory, i^./f., 
F,n.S., c^c* 

/^LAIRAUT's principle alluded to, has all the precision 
^^ and elegance which are admired in the applications of 
the ancient geometry, such as are found in the writings of 
Aixhimedes. It might not be useless to inquire how it hap- 
pens that geometers, neglecting the elegant method of Clair- 
aut, have so generally agreed in giving the preference to the 
theory of Euler, grounded on the equality of pressure which 
necessarily takes place in every fluid at rest, whatever be the 
causes by which such a state is induced. It would, no doubt, 
be found that this is owing to the great generality of the 
equations of Euler's method, which are easily obtained, and 
seem to embrace every proposed problem and to reduce it 
immediately to a question of abstract mathematics. 

Clairaut begins with supposing a mass of fluid in equili- 
brium, thus laying a sound foundation for his reasoning. The 
forces at the several points of the supposed mass, which may 
be called A, being expressed in numbers, he next spreads 
over the surface of A, a thin stratum 8 A, so as to fulfil the 
condition, that the force at any point of the surface of A mul- 
tiplied by the thickness of S A at the same point, shall con- 
stantly make the same product. This being done, when the 
quantities of the matter of the stratum on which the forces 
act are taken into account, it follows that every infinitesimal 
portion of the surface of A, will sustain a proportional press- 
ure ; so that the intensity of pressure, estimated on a given 

* Communicated by the Author. 
Phil. Mag. S. 3. Vol. 13. No. 83. Nov. 1838. Y 



322 Mr. Ivory on the Figure of Equilibrium of a Fluid, 

surface, is invariably the same over all the surface of A. 
Now the supposed equilibrium of A will not be disturbed by 
pressures of the same intensity exerted at all the points of its 
surface; and therefore a new body of fluid in equilibrium, 
namely, A + SA, is obtained. Continuing to reason in like 
manner, the original mass A may be enlarged to any dimen- 
sions by the addition of successive strata, at the same time 
that an equilibrium is preserved at every step. It is easy to 
make the procedure independent of the fii'st supposition, that 
A is in equilibrium ; for as the reasoning holds whether A is 
great or small, we may suppose it so small that any forces 
inherent in its own particles and tending to change its figure, 
are overpowered and annihilated by the accumulated pressure 
of the incumbent strata. 

When the property of equilibrium, demonstrated in these 
few words, is put in equations as Clairaut has done, these 
equations are found to be the very same as those deduced 
from Euler's theory. Thus, in point of application, the two 
methods are entirely equivalent : if one is capable of solving 
a problem, the other may be used with equal success. 

The investigation of Clairaut is clear and definite. It evi- 

1 • 

dently assumes that there is no cause tending to disturb the 
equilibrium of A, except the action of the forces at the sur- 
face of A upon the matter of 8 A. On this account his me- 
thod fails when there is a mutual attraction between the mass 
A and the stratum S A. If the mass A attract the matter of 
the stratum 8 A and cause it to press, it follows necessarily 
that the matter of 8 A will react, and, by its attraction, will 
urge the particles of A to move from their places. In this 
case therefore the equilibrium of A is disturbed by a cause 
which Clairaut has not attended to ; and unless the effect of 
this new force is counteracted, the body of fluid A + S A, will 
not be in equilibrium. The principle of the method suggests 
a remedy for this omission ; for it is easy to prove that the 
equilibrium of A will not be disturbed by the attraction of the 
stratum 8 A, if the resultant of that attraction upon every 
particle in the surface of A, be directed perpendicularly to 
that surface, And thus we arrive at the same two inde- 
pendent conditions for the equilibrium of a fluid consisting of 
attracting particles, which have been found necessary in every 
other way of solving the same problem when nothing essen- 
tial is neglected. (Vide this Journal for August last, p. 81, 
and for October, p. 274.). 

The principle of Clairaut's method, when enunciated ge- 
nerally, lies in this, that the supposed equilibrium of A is not 
to be disturbed by the addition of a stratum ; and therefore 



the Particles of which are urged hy accelerating Forces. 323 

in applying it, every force which is introduced by a stratum 
and is capableof moving the particles of A, must be carefully 
ascertained and made ineffective. 

The method of Clairaut, as it has been explained and ex- 
tended, will help us to form a just notion of Euler's theory. 
A very little attention will show, that all the perplexities 
that have ever attended this theory, originate in misconcep- 
tion of the manner in which a particle of a fluid in equilibrium 
is made immoveable by the pressures which act upon it. 
If we conceive a particle placed on one of the interior sur- 
faces in Clairaut's method, that is on a level surface, it is most 
evident that all the pressure upon the particle is caused by 
the action of the fluid above it, or on the outside of the level 
surface. If the fluid without the level surface were removed, 
there would be no pressure upon the particle, which would 
only be subject to the action of the forces inherent in the sur- 
face on which it is placed. Now pressures of equal intensity 
are impressed at all the points of a level surface; these press- 
ures are transmitted through the contained fluid to the par- 
ticles on the surface ; so that every such particle is pressed 
equally in all directions by the action of the fluid exterior to 
the surface. It is therefore correct to say that a particle in 
a level surface is not moved by the pressures caused by the 
forces which urge all the fluid on the outside of that surface : 
but this does not demonstrate that the particle is at rest by 
the action of the whole mass. To complete the proof of an 
equilibrium, it is further necessary to show, that the body of 
fluid within the level surface is not liable to a change of its 
form or position by the forces that act on its own particles. 
The theory of Euler is therefore chargeable with mistaking 
the action of a part only of the fluid, for the effect of the 
forces that urge all the particles of the mass. If a canal be 
drawn in any manner from a particle in a level surface to ter- 
minate in the upper surface, it will invariably exert the same 
pressure upon the particle: but the nature of a level surface 
is such, that a part of any canal within it presses neither 
way ; so that the pressure upon the particle is produced solely 
by the action of the forces upon the part of a canal exterior 
to the level surface. We may now safely affirm that the 
great generality of Euler's theory arises from omitting what 
is essential to an equilibrium ; and enough has been said to 
show that, when the omission is supplied, we arrive at the 
principles of Clairaut's method by a route which is different 
indeed, but not so direct. 

One observation more it seems requisite to make. Euler 
has investigated his theory in a memoir {Mem. de Berlin^ 

Y2 



324? Mr. Ivory o« the Figure of Equilibrium^ 8^c. 

1755) which cannot be enough admired for invention and all 
the qualities of the highest mathematical genius, if we over- 
look the too precipitate adoption of a principle seducing by 
its great generality. But the equality of pressure seems to 
have been first used in solving this problem by Maclaurin. 
If we strictly appreciate what that great geometer has pi'oved 
in his celebrated demonstration, it will be found not only not 
inconsistent with what has been said, but to acquire force and 
simplicity when stated according to the foregoing principles. 
Taking any particle of the fluid spheroid, Maclaurin proves 
that any rectilineal canal standing upon it and terminating 
in the upper surface, urges it to move with a force equal to 
the effort of the fluid in the difference of the polar semi-axes 
of the proposed spheroid and a similar one, the surface of 
which passes through the particle. (Fluxions, § 639). Now 
this does not prove that the particle is at rest by the equal 
pressures upon it ; but, on the contrary, that it may have any 
position on an elliptical surface without any variation of the 
pressures which urge it. It follows indeed that all the par- 
ticles on the same elliptical surface are in equilibrium rela- 
tively to that surface, that is, there is no force urging them 
to move upon it ; but, even when this is attended to, another 
condition is still wanting to prove the immobility of the par- 
ticle relatively to the whole spheroid, which is, the stability, 
both in form and position, of the elliptical surface which con- 
tains the particle. These observations being duly weighed, 
it is obvious that all the inferences from what Maclaurin has 
proved, are deducible from the equality of pressure at all the 
points in the surface of every interior elliptical spheroid, con- 
centric and similar to the given one ; which is according to 
Clairaut's principle. 

In his work on the Theory of the Earth, Clairaut has 
adopted the method of Maclaurin in preference to his own 
theory, of which he makes little use. In reality the equili- 
brium of a homogeneous planet in a fluid state cannot, by 
strict reasoning, be deduced from his method according to 
the exposition he has given of it ; because the reaction of the 
strata on the masses on which they are laid is neglected. 

Oct. 15, 1838. James Ivory. 



[ 325 ] 

XLIII. On a new Compound of Sulphate of Lime *with 
Water. By James F. W. Johnston, F.R.S., Sfc. ^c* 

T N the boiler of a steam-engine worked at Team Colliery 
-*- near Newcastle, and fed by water from the mine, a bright 
steel-gray granular deposit has been several times observed, 
which under the microscope appears to consist of small trans- 
parent prismatic crystals discoloured by carbonaceous matter. 
The faces of these crystals are rounded, but according to 
Mr. Brooke, they are right rhombic prisms, the angles being 
undeterminable with any degree of accuracy. 

Heated in a close vessel these crystals give off pure water, 
becoming opake, and at a red heat in the air they lose their 
colour and become white. Heated to 220° Fahr. in the air 
they lose a sensible quantity of water, and kept at 240° Fahr., 
for a couple of hours the whole of the water is driven offj so 
that at a higher temperature they undergo no further loss, 
except what is due to the combustion of the small quantity 
of carbonaceous matter they contain. 

Boiled in distilled water they are very sparingly soluble : the 
solution gives white precipitates with chloride of barium and 
oxalate of ammonia. 

After drying at 212°, ] 9-424' grs. lost 1"25 = 6-435 per 
cent, when heated in a close vessel till all the water was driven 
off. The colour was still gray. Heated to redness in the air 
till it became white, the loss amounted to 6*728 per cent., 
giving 0*293 per cent, for carbonaceous matter. A second 
portion of 25*194 lost 1*742 when heated to redness in the 
air = 6*914 per cent. 

Of the white salt thus heated in the air, fused with car- 
bonate of soda, digested in distilled water, filtered, and pre- 
cipitated by chloride of barium, gave 

Anhydrite by calculation 
contains 

Lime 41'734 41*532 

Sulphuric acid ... 59*027 58*468 

The salt therefore consists of 

Sulphate of lime = 93*272 

Water = 6*435 

Carbonaceous matter = 0*293 100* 

The formula Ca S + 4 H gives 

Sulphate of lime = 93*843 

Water = 6*157 100* 

• Communicated by the Author. 



326 Prof. Johnston on a new Compound of 

'^^! yj^fi\g^^^^^y «f '^^ "^^ ^^^'1 = 2-753 and 2-76 1 
at 60 i^ahr J 

After heating to redness = 2*936 and 2*929 

Its density, therefore, as we should expect, lies between 

those of gypsum and anhydrite, and after heating to redness 

it has precisely the specific gravity of the latter. 

Density of gypsum = 2*310 Mohs, 2*322 Royerand Dumas. 

new salt = 2*757. 

anhydrite = 2*899 Mohs, 2*96 Royer and Dumas. 

r new salt-1 ^ 2*932. 

alter heatmg j 
The boiler in which this deposit is formed is worked under 
a pressure of nearly two atmospheres, and to this among other 
circumstances is probably due the formation of this sin- 
gular hydrate. When sulphuric acid is added to a dilute 
boiling solution of chloride of calcium, crystals of gypsum 
with the usual quantity of water are deposited. Added hot 
to a solution of chloride of calcium which boiled at 265° Fahr., 
an earthy precipitate fell, which after drying at 212° lost by 
a red heat only 1*43 per cent. The temperature of a more 
dilute solution boiling at a heat of 220° to 230° Fahr. falls in- 
stantly to 212° Fahr., on the addition of a drop of hot sul- 
phuric acid ; the sulphate formed causing a copious evolution 
of vapour. I have therefore not succeeded in my attempts 
to form this salt artificially. The uniform high temperature 
maintained under a higher pressure than that of the atmo- 
sphere may be the chief cause of the formation of the salt in 
the steam boiler. 

Is this salt a simple hydrate 2 Ca S + H, or is it a com- 
pound salt Ca S + Ca SH, or 3 Ca S + (Ca S + 2 H) ? This 
question is entirely theoretical, the properties of the salt 
lending no direct support to either opinion. It is, however, 
not without interest in the present state of our knowledge in 
regard to the water contained in salts. The observation made 
in regard to the superior affinity of many sulphates for one in 
preference to the other atoms of water which their crystallized 
hydrates generally contain, does not apply to the sulphate of 
lime, and the existence of this half hydrated crystalhzed com- 
pound — if considered as a simple salt2CaS + H — is equally 
inconsistent with the idea expressed by the term saline water. 
If by this term it is intended to denote that of the 6 or 7 
atoms of water with which certain sulphates combine, one of 
these equivalents performs a peculiar function, we have in 
the present salt half an atom only remaining, and this driven 



Sulphate of Lime with Water. S27 

off with nearly the same ease as any of the water is driven off 
from gypsum. It may however be a compound of anhydrite 

with gypsum or with the monohydrate Ca SH, in which case 
its constitution may be reconciled with the theoretical views 
of Professor Graham. 

That the relations of sulphate of lime to water do not form 
an exception to the general laws by which those of the other 
sulphates belonging to the same isomorphous group are re- 
gulated, may be inferred from the discovery by Mitscherlich, 

of a sulphate of iron (Fe S + 2H) analogous in constitution 
with gypsum, and like it possessed only of a sparing solubility. 
This analogy leads us rather to expect other compounds of 
sulphate of lime with water analogous to those observed in 
the sulphates of iron, magnesia, &c. and that the changes 
produced on the analogous hydrated salts of each of the sul- 
phates by heat and other agents should be generally the 
same. 

There are strong grounds for accepting it as a general con- 
clusion that whatever compound has been formed by one 
member of an isomorphic, may be formed, under other circum- 
stances perhaps, by every other member of the same group. 
If we compare what we know with what on this prinicple is 
possible, we shall find our real knowledge to be unexpectedly 
small. It is something, however, to know how much in a 
particular line remains yet to be discovered. Even in the 
branch of saline compounds which has received so general 
an attention from chemists, and for so long a period, a com- 
parison of this kind is calculated to astonish us by the vast 
number of compounds it exhibits as remaining yet to be 
sought for. 

Let us take for example the class of hydrated sulphates to 
which gypsum belongs, and compare the known with the pos- 
sible, as is done in the following table. 

In this table 81 compounds are indicated, while of these 
only 18 are actually known to us, or less than one fourth 
part, while many more may still be possible belonging to the 

formula R S + 4 H, and the various formulae intermediate be- 

tween seven and twelve atoms of water (RS + 7H and RS 

+ 12H). 

The general formulae at the heads of the columns indi- 
cate the crystalline compounds believed to be possible, the 
special formulae underneath the crystalline compounds actu- 
ally known. 



328 



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Mineral Substances of Organic Origin. Guyaquillite. 329 

Suppose our actual knowledge of the almost countless 
groups of salts already partially studied to be tabulated in a 
similar manner, and thus compared with the unknown, how 
few would the cultivated spots appear, how large the water 
yet to be reclaimed ! And whenever we consider how very 
few of the properties of the salts longest known have yet 
been determined with any degree of accuracy, how mere a 
skeleton does all our chemical knowledge appear ! We hasten 
after new conquests without waiting to consolidate our do- 
minion. 

The existence and mode of formation of this salt throws 
some light on a point of geological interest. As anhydrite 
occurs only in connexion with rock-salt, it was suggested 
by Berzelius that the latter might be an igneous and not an 
aqueous deposit*. Deposited in water the sulphate of lime 
ought, he reasoned, to be in the state of gypsum, and not of 
anhydrite ; but the formation of the hemihydrated salt above 
described, shows that the quantity of water present in such 
salts does not depend on the presence or absence of water 
only, but on the united temperature also inider which the 
crystals are formed. Had the pressure in the boiler been so 
great as to raise the temperature to 260° Fahr. anhydrite 
would be formed in nature as it was formed on pouring sul- 
phuric acid into a solution of chloride of calcium boiling at 
265° Fahr. 

Two fragments from the exterior of an apparently pure 
mass of anhydrite from Germany lost when heated to redness 
about 6 per cent, of water. The interior of the mass lost a 
mere trace. Does this show any tendency in anhydrite to 
form the new compound ? 
Durham, June, 1838. 

XLIV. On the Composition of certain Mineral Substances 
of Organic Origin. By James F.W.Johnston, A.M., 
F.R.SS. Lond. and Ed., F.G.S., Professor of Chemistry and 
Mineralogy, Durham.f 

VI. Guyaquillite. 

T AM indebted to Mr. Brooke for a small quantity of a re- 
-*• sinous substance said to form an extensive mineral deposit 
in the neighbourhood of Guyaquil in South America, and for 
which I propose the name of GuyaquiUite. 

Of this substance I have seen two varieties, one nearly ho- 
mogeneous of a pale yellow colour, with no resinous lustre or 

• See note If in the preceding page. f Communicated by the Author. 



330 Prof. Johnston on the Composition of certain 

fracture, not compact, but as if made up of many small por- 
tions adhering together. The other variety is mixed with a 
greater or less quantity of a dark brown, bituminous-like 
substance interposed between the small fragments of which 
the mass is composed. 

The pure mineral is opake, of a pale yellow colour, yields 
easily to the knife, may be rubbed to powder ; is very slightly 
soluble in water, and largely in alcohol, giving yellow solu- 
tions which have an intensely hitter taste. This last property 
is highly characteristic. By slow evaporation the alcoholic 
solution yields pale yellow prisms. As it occurs in nature, 
the Guyaquillite has a sp. gr. of 1*092; after fusion, it may 
possibly be a little heavier. 

It begins to melt at ] 57° Fahr., but continues viscid, and 
does not flow easily till near 212°. As it cools it adheres to 
the finger and exhibits much tenacity, forming fine threads 
when drawn out. After fusion it is semitransparent, a little 
darker in colour, and exhibits the resinous fracture and lustre. 
Heated in a close tube over a lamp, it darkens, is decomposed, 
and yields empyreumatic products. 

It dissolves readily in a dilute solution of caustic potash and 
less so in caustic ammonia, giving yellow solutions, from which 
it is again precipitated by an acid. Sulphuric acid of com- 
merce dissolves it in the cold, giving a dark reddish brown 
solution, from which water throws down the resin apparently 
unchanged. Muriatic acid boiled over it becomes yellow, but 
dissolves very little and does not appear to alter it. Strong 
nitric acid by the aid of heat acts upon it with the evolution of 
red fumes, becoming yellow. It dissolves it, however, in small 
quantity only, and the solution becomes milky as it cools, and 
deposits white flocks. It is also precipitated white by the 
addition of water. I have had too little of the substance to 
permit me further to investigate the nature of the change 
produced by this acid. 

The action of liquid ammonia on the alcoholic solution of 
this substance is characteristic. The pale yellow solution, by 
the addition of a few drops of ammonia, gradually darkens, 
and ultimately becomes dark brownish red. The alcoholic 
solution gives a yellow precipitate, with a similar solution of 
acetate of lead. With one of nitrate of silver it gives at first 
none, but after standing for several hours a small quantity of 
a very dark precipitate shows itself. The addition of am- 
monia determines a brown precipitate, which speedily darkens 
and assumes a deep purple or black colour. This mineral 
substance, therefore, like the resin of retin asphalt (retinic 
acid), belongs to the class of acid resins. 



Mineral Substances of Organic Origin. VI. Guyaquillite. 331 

Burned with oxide of copper from which the moisture had 
been well pumped out, 

7*538 grs. gave 20*9 grs. of carbonic acid and 5*54-5 of water. 

, 8-415 grs. — 23*54<grs. 6-208 

These are equivalent to 

I. II. 

Carbon = 16-665 77*350 

Hydrogen... = 8*174 8-197 

Oxygen = 15*161 14-453 

100* 100* 

The formula Cgo H,3 Og gives the proportions 

20 C = 1528*750 = 76*783 

13 H= 162*2348 = 8*148 

3 O = 300-000 = 15*069 



1990-9848 100* 

It is difficult to determine what is the rational formula of 
this compound. It may either be an oxide 

^20 Hi3 + Og, 

or a hydrate C20 Hjo + 3 H O, 

Q in which 

three equivalents of hydrogen are replaced by three of oxy- 
gen. 

The ratio of the carbon to the hydrogen, 20 : 13, renders it 
unlikely that it is a simple oxide ; and that it is not a hydrate 
is rendered very probable by the fact that the ratio of these 
two elements remains the same in the guyaquillate of silver. 

Thus a portion of a silver salt of a dark colour gave on 
burning with oxide of copper, 

Carbon = 17*675 = 20 atoms. 

Hydrogen ... = 4*754 = 13*22 atoms. 

{ — 3 H 
Q or simply 

C20 Hjg Og, gives the most probable representation of the true 
constitution of this substance. Of course the relation to oil 
of turpentine indicated by the formula, though interesting and 
agreeing with the doctrine of substitutions, must be viewed 
with distrust, till the geological position and probable origin 
of the mineral be more fully investigated. It is easy to sup- 
pose it, like amber, of vegetable origin, and to occur in consi- 



332 Mineral Substances of Organic Origin. Guyaquillite. 

derable quantities on the site of ancient forests of resiniferous 
trees; in which case the connexion with oil of turpentine 
would be at once beautiful and easily understood ; but if it 
occur, as is said to be the case, in extensive layers, its imme- 
diate source is not so easily understood. Were it volatile 
without decomposition we could also account for its sublima- 
tion like sulphur, or its distillation like petroleum by the 
agency of the volcanic heat so extensively diffused beneath the 
iSouth American continent ; but as the affinity of its elements 
appears to be overcome by a comparatively moderate tem- 
perature, we must still remain in doubt as to whether in its 
present state it is to be considered as more immediately or 
more remotely of vegetable origin. At the same time it is 
worthy of remark, that this is not the only instance of a true 
resin being said to occur in large quantity as a mineral pro- 
duct in South America. I have in my possession a specimen 
of a peculiar dark-coloured resin, which, as my friend Mr. 
Fryer of Whitley-house, informs me, is found in a species of 
pitch lake in the desert of St. Juan de Barengela, and is 
thence transported in large quantities to the coast for the use 
of the shipping. Of this substance I shall give a description 
and analysis in a future communication. 

Guyaquillate of Silver. — To determine the atomic weight 
of this resin, I prepared several portions of the salt of silver. 
It appears, however, to form, in common with most of the 
acid I'esins, both neutral or acid and basic salts, as I have been 
unable in the several trials which the quantity of the substance 
at my disposal permitted me to make, to obtain two portions 
of preciselj^ the same constitution. This may also have arisen 
partly from the necessity I have been under of using the less 
pure variety for solution, as my supply of the unmixed was 
exhausted. The mixture however consists in great part of 
a bituminous matter insoluble in alcohol. 

1. Of a portion which had subsided gradually on the ad- 
dition of ammonia and was perfectly black, 6*7 19 grs. left 
4*728 grs. of metallic silver = 75*573 per cent, of oxide. 

2. A portion of a second preparation gave only 68*86 1 of 
oxide ; but this was evidently a mixture, for when boiled again 
in alcohol and collected on the filter it gave 72*266 per cent, 
of oxide of silver. These two results indicate an equivalent 
= ^ (C20 Hj3 O3), since a compound represented by \ (Cgo 
H13O3) +AgO would contain 74*512 per cent, of oxide. 

3. The hot alcohol in which No. 2 was boiled, deposited 
on cooling a brown precipitate, which gave on burning only 
14*939 per cent, ofoxide of silver. 



Mr. Laming ofi the primary Forces of Electricity. 333 

4 (C20 Hi3 Og) + Ag O contains 14*417 per cent, of oxide. 

4. A third portion separately prepared, which was brown 
when precipitated, but had become black, gave 26*888 of 
oxide of silver. 

2 (CgoHia 03) + AgO contains 26*715 of oxide of silver. 

We may conclude therefore that this acid forms different 
classes of salts with the same base, which possess different de- 
grees of solubility ; the conditions necessary to ensure the 
constant production of the same compound, and the determi- 
nation of which are the neutral and which the acid or basic 
salts, will require further investigation. 

Durham, June, 1838. 

XLV. On the primary Forces of Electricity . By 
Richard Laming, Esq.^ M.R.C.SJ^ 

[Continued from p. 54,] 
Part 11. 
66. TT may be useful before we proceed to consider the 
-B- origin and propagation of induction among the atoms 
of contiguous bodies, to recapitulate some of the chief parti- 
culars in the new theory which are thought to be established 
as facts in the preceding part of this paper. 

1st. The attraction which is reciprocal between electricity 
and common matter is definite with regard to quantity 
as well as force ; no kind of matter ever attracting either 
more or less of electricity than the quantity which con- 
stitutes its natural equivalent (3.). 
2ud. Besides the above force, designated the major elec- 
trical attraction, there is a second by which the atoms of 
electricity are associated together; and this we have 
called the minor electrical attraction (IS.)* 
3rd. The minor electrical attraction is the alone cause of 

bodies becoming plus or positively electrical (16.). 
4th. Electrical induction is immediately dependent on the 

definite nature of the major electrical attraction (7.). 
5th. The electrical condition of a body under induction 
virtually or really compensates the opposite electrical 
state of the inducing body (11.). 
6th. Induction, and consequently compensation, in all cases 
precede the sensible locomotion of matter caused by the 
action of the major electrical attraction ; whether it be 

* Communicated by the Author. — Erratum, p. 45. Art. 34, eighth line, 
for " as the densities of the air directly," read '* as the densities of the air 
inversely." 



334! Mr. R. Laming 071 the 'primary 

that of free electricity moving towards its minus com- 
pensator, or of common matter, either plus or minus, 
moving towards other common matter in the converse 
electrical condition. 

7th. Electrical discharges are always more or less retarded 
by the action of the minor electrical force in the plus 
body (43.). 

8th. Free electricity maybe conducted by the inductive in- 
fluence of the major force from plus to minus bodies 
(54.55.60.61.). 

67. In addition to these several facts it was shown that the 
law of Coulomb is the law of the major electrical force ; and 
by necessary inference of electrical induction also. Hence it 
follows that no mass of common matter can be dispossessed 
of the least portion of its natural electricity by the major force 
of free electricity acting on it at a sensible distance ; and thus 
we learn at once that induction can only be established on 
contiguous atoms. 

The manner in which induction is originated will almost 
immediately be brought under consideration ; but we purpose, 
on the assumption of its existence, to trace first the mode of its 
propagation among contiguous atoms. 

68. We have seen that whenever by virtue of the minor 
force free electricity is attached to an insulated body, that 
body must be surrounded by an insulating medium either ac- 
tually or virtually in a minus electrical condition (32.) ; if we 
conceive the plus body to be a sphere freely insulated in the 
atmosphere, the spherical stratum of aerial atoms immediately 
in contact with it will, in order to compensate its charge, vir- 
tually dismiss portions of their own natural quantities; but 
the dismissal being only virtual and not real, this first stratum 
will become plus also (12.); a second spherical stratum of 
aerial atoms, by compensating the former, will in their turn 
become plus ; and these in like manner impress a similar con- 
dition on a third ; the third on a fourth, and so on ad in- 

Jinitum, or until the action be terminated by the presence of 
some uninsulated body capable of actually dismissing the re- 
quisite portion of its natural electricity. 

69. Now if the uninsulated and really minus compensator 
be free to move, its common matter, being attracted by the 
virtually plus air compensated by it, will receive an impulse 
in the direction of the charged sphere. After moving a little, 
the uninsulated body will assume the compensation of, and 
therefore be attracted by, the inner portion of air next con- 
tiguous; then moving again it will approach a third, and 



Forces of Electricity, Part II. 335 

other successive portions of air, until it is brought to rest 
against the charged sphere itself, by which the whole line of 
inductive action was occasioned. 

70. As it is with visible attraction, so also is it in the case 
of electrical discharges ; the free electricity is attracted on- 
ward towards the uninsulated compensator by each of the 
aerial strata in succession, until at length attaching itself to 
the former it returns to a state of natural equilibrium. 

71. These principles enable us to understand that neither 
the discharge of free electricity which we may observe to take 
place from plus to minus bodies, nor the reciprocal attraction 
of such bodies by one another, is affected by any direct action 
they might be supposed to have on one another, but, on the 
contrary, through the medium of intervening matter; conse- 
quently it is only in a restricted sense that we may speak 
of distant bodies compensating or attracting one another. 
Hence the law of Coulomb must be received only as conven- 
tional, for although it embraces phgenomena with accuracy, 
it is palpably fallacious in theory. 

72. We have it in our power, by a very simple method, to 
verify the conclusion respecting the contiguous action of in- 
duction, to which we have thus been conducted by the theory. 
It is in principle as follows : let a plus body be separated from 
its compensator by an insulating medium of determinate 
thickness, and the electrical condition induced in the com- 
pensator be estimated in the ordinary manner by an electro- 
meter. Then, if induction be independent of the insulating 
medium, the merging of a second equally plus body, and also 
of a second similar compensator, in the first respectively 
should add nothing to the intensity of the induced charge; 
or to reduce the case to practice, the capacity ofaLeyden jar 
should increase with the thickness of its metallic coatings, 
minus some little on account of the minute increase in their 
mean distances. Now I find, and I believe the fact to be suf- 
ficiently notorious, that a given electrical charge on one of the 
coatings of a Leyden pane will exhibit precisely the same in- 
tensity whether the coatings be composed of films of Dutch 
metal only, or the very much thicker leaf of tinfoil, even 
though it be several times repeated. 

73. The view of induction now presented opens up to us 
the cause of Coulomb's law ; thus advancing us in knowledge 
another step towards that incomprehensible link which con- 
nects the immaterial impulse of the Divine Will with the 
material creation. To understand this cause let us imagine a 
quantity of free electricity to be accumulated in an insulated 



336 Mr. R. Laming on the primary 

point and surrounded by concentric strata of a compensating 
atmosphere (68.) ; then, the strata being all of equal thick- 
ness, either will contain a number of electrical atoms varying 
directly as the square of its distance from the centre. Now, 
assuming, what is strictly agreeable to sound reasoning, that 
the induction on any stratum is equally distributed among all 
the atoms contained in it, and knowing from the definite na- 
ture of the major electrical force that the sum total of the in- 
ductive force exerted by the charge is a constant quantity in 
each of the strata, it must of course follow that the force upon 
any given atom, in either of the strata, is as the square of its 
particular distance from the centre inversely. 

74. Having thus shown that induction is extended to bodies 
at sensible distances by the intervention of others in imme- 
diate contiguity, we may proceed to investigate the manner of 
its origin ; and for this purpose it is requisite to trace more 
minutely than we have yet had occasion to do, the connection 
of the electrical with common atoms. 

75. It will doubtless be admitted that if the principles we 
have hitherto advocated be in the general consistent with 
facts, each atom of common matter is enveloped in an atmo- 
sphere of electrical atoms; or as we shall find it convenient 
to express it, each common atom constitutes a centre of major 
electrical force to an electrosphere. Now without entering 
here into the question of the relative volumes of these electro- 
spheres, it will be sufficient for our present purpose to ex- 
amine the manner in which they generally are connected with 
common atoms, and the reciprocal action under particular 
circumstances of such as are of equal volume. 

76. In the first place it may be pi'emised, that we have no 
reason for asserting that the major force which is reciprocal 
between a common atom and the electrical atoms which form 
its equivalent electrosphere, observes the law of Coulomb : for 
the inductive action on which that law depends obviously 
commences at the surface of the electrospheres ; on the other 
hand it will be admitted that this fact supplies no argument 
against such a supposition ; and at all events we are quite 
sure, whatever be the ratio, that those atoms of an electro- 
sphere which are nearer to the central nucleus are attracted 
with the greater forces ; for were it not so the retarding forces 
to the compensation of successive increments of free electri- 
city to a plus body could not progressively increase as we 
have already proved them to do (6.) . 

77. This being understood we may proceed at once to our 
task. Let us conceive the electrical equivalent of an atom of 



Forces of Electricity: Part II, 337 

common matter to surround it in the form of any number of 
concentric strata; the major force of the central nucleus upon 
all the electrical atoms will then vary in some unknown ratio 
inversely as their distances respectively. Hence an atom of 
free electricity attracted to the surface of such an electro- 
sphere by the minor force, being necessarily the most distant 
atom, and, so far as the equivalent of the common atom is\ 
concerned, supernumerary, could never become attracted by 
that common atom ; under such circumstances, therefore, the 
free atom would exercise no inductive action whatever to 
cause any portion of the contents of the electrosphere to be- 
come liberated. 

78. Now let us suppose the preceding case to be repeated, 
with this only modification, namely, that the outer stratum of 
the electrosphere by which the electrical equivalent of the 
common atom is completed were deficient some one or more 
of the number of electrical atoms requisite to constitute it a 
perfect shell ; and we shall find the result to be very different. 
To fix and simplify our ideas, let us imagine the electrical 
equivalent to be completed by the existence of a single elec- 
trical atom on the surface of the last perfect stratum of the 
electrosphere, and an atom of free electricity to be artificially 
placed against that surface; in such a case two electrical 
atoms would obviously be at the same distance from the centre, 
and consequently the more proximate hemisphere of each 
engage the major force of the common nucleus. 

79. In the next place let there be a second similar electro- 
sphere in contact with the former one ; the tendency of the 
two exterior electrical atoms, as also that of the added free 
atom, under the influence of the minor force, will be to place 
tiiem all in a triangular position in a plane separating the 
two electrospheres. Whether in this or any other situation, 
two of them will be equally held by the major force of the two 
common nuclei, each of the latter acting on proximate hemi- 
spheres; the third atom of electricity being retained in con- 
nection simply by the minor force. 

80. But as in electrical investigations we experiment not 
with atoms but with masses, we have to modify this view of 
the positions of the exterior atoms of the electrical equivalent. 
If a homogeneous body be composed of electrospheres similar 
to those last imagined (78. 79.), the exterior electrical atoms 
of the electrospheres, considered generally, will be equidistant, 
or nearly so, from one another, being equally attracted in 
opposite directions by the minor force in contiguous electro- 

Phil. Masr. S. 3. Vol. 13. No. 83. Nov. 1838. Z 



338 On the primary Forces of Electricity : Part II. 

spheres *; consequently the natural position of a line of such 

electrospheres will be as shown in the annexed figure, in which 

the points repi'esent the nuclei of 

common matter; the larger circles Fig. 3. 

the boundaries of the perfect strata of ,.„,„, ..u ,.u 

, , , ^ , , ,, 1st. 2nd. 3rd. 4th. 5th. 

the electrospheres ; and the smaller r^-'^~\r^/^.\'^'\ 
circles the exterior atoms of electri- ^^■••Z.^\iJ\iJ\l.)\ ' j 
city by which the equivalents of the 
common nuclei are completed. 

81. Now, on presenting to the first of such a line of electro- 
spheres any body in a plus electrical condition, it is quite ma- 
nifest by the principles we are examining, that the major force 
will induce the exterior atom of the first electrical equivalent to 
take the place of the second, this of a third, and so on, to 
the end of the line where the exterior atom will appear free ; 
or otherwise it will be found at that place in the series where 
it can obtain the most perfect compensation, and beyond 
which of course the inductive process would not be con- 
tinued. 

82. If we conceive the last electrosphere in the line to be 
so circumstanced, with regard to contiguous bodies that it can 
give off its exterior and free atom as rapidly as it becomes 
replaced, the inductive action just described may be repeated 
an indefinite number of times, or so long as the plus electrical 
body at the other extremity retains a single free atom to com- 
plete the equivalent of the proximate electrosphere. In this 
case the whole line performs the function of a conductor of 
electricity. 

8r5. Inasmuch as induction and compensation are always 
simultaneous they may in a certain sense be regarded as syn- 
onymous terms ; but for sake of theoretical precision it will 
be useful not only to regard the latter as the effect of the 
former, but also to subdivide compensation into virtual and 
actual. By virtual compensation we should understand that 
state of a given body, in which, though exactly retaining its 
natural electrical equivalent, it exhibits under the influence 
of induction the characteristics of a charged body ; and by 
actual compensation we might describe that other condition 
in which a body is placed by induction when it really pos- 
sesses a quantity of electricity different to its natural equiva- 
lent. 

84. If our explanation of the origin of the inductive pro- 

• The agency by which electricity is made elastic is here assumed to be 
in operation ; its nature will be the subject of a future communication. 



Prof. Apjohn on the Specific Heats of the Gases. 339 

cess be expressive of the truth, we shall perceive, first, that 
the susceptibility to induction in electrospheres will increase 
with the number of electrical atoms in their external and im- 
perfect strata, so long as the number is not too great for all 
of them to be equidistant from the two contiguous central 
nuclei ; and, secondly, as the limited number will be greater 
as the electrospheres are more voluminous, that the in- 
ductive susceptibility will be the more exalted as the electro- 
spheres are larger. Now we have found reason to believe 
that induction, as evidenced by compensation, increases with 
the atomic weights of bodies (28.); and if this be true, the 
conclusion to be deduced from the fact obviously is, that the 
volumes of electrospheres vary as their weights, or in other 
words, that the minor electrical force is the cause of gravita- 
tion. 

85. The justness of such a conclusion will be made more 
apparent in the next part of this treatise ; in which we shall 
endeavour to show that the principles we have promulgated 
are adequate to explain all the phaenomena of electrical ex- 
citation. 

[To be continued] 



XL VI. The Spectre Heats of the Gases as deduced by Dr. 
Apjohn, compared with the more recent Results qf Dr. 
Suerman. By James Apjohn, M.D., M.R.I.A., Professor 
of Chemistry in the Royal College of Surgeons, Ireland. 

[Continued from p. 273, and concluded.] 

A T the close of the paper which I have submitted to the 
-^^ Royal Irish Academy, I have hazarded the following pro- 
positions, which would seem to be justified by the results of 
my researches. 

1. The simple law so much insisted upon in modern times 
by Haycraft, Marcet, and De la Rive, and others, that equal 
volumes of the different gases have the same specific heat, is 
not the law of nature. 

2. The more limited conclusion announced by Dulong, 
that the simple gases have under equal volumes the same spe- 
cific heat, is probably not true in a single instance, and is al- 
together at variance with my result for hydrogen. 

3. The numbers at which I have arrived correspond tole- 
rably well with those of De la Roche and Berard except in 
the case of hydrogen, to which I ascribe a specific heat greater 

Z2 



S-l-O Prof. Apjohn on the Specific Heats of the Gases, 

than that assigned to it by these philosophers in the ratio very 
nearly of 5 to 3. 

4. There does not seem to be any simple relation between 
the specific heats of the gases and their specific gravities, or 
atomic weights, and philosophers in searching for such are 
probably pursuing a chimera. 

From this exposition of my method, and summary of my 
experiments, I now turn to the more recent researches of 
Suerman. These researches have appeared in the form of 
an inaugural essay, which was published by the author upon 
the occasion of his taking a degree in the university of 
Utrecht. He had, he informs us, for a long time determined 
upon making the specific heats of the gases the subject of his 
thesis ; but when after many interruptions he had at length 
begun to provide himself with the necessary apparatus, he 
was much chagrined at finding, upon looking into a re- 
cent number of the Philosophical Magazine, that I had al- 
ready investigated the same question, and by the very method 
which it was his intention to have employed. He would, in 
fact, have turned to something else were it not for the per- 
suasions of Professor Moll, who urged him strongly to per- 
severe in his undertaking. This he was fortunately induced 
to do, and the result has been a most elaborate and lucid hi- 
story of the various attempts which have been made towards 
the solution of this very difficult problem in physics, followed 
by a detailed account of a number of experiments instituted 
by himself with a similar object. 

His method I have stated to be the same with that which 
I had previously adopted. This is strictly true. The formula, 
however, which he used in calculating his observations, and 
which he stated to be due to Gay-Lussac, is slightly different 
from that which I have employed. In part retaining the 
notation already used, and slightly changing the form of his 
expression, it will become 

_ fe SO 

an equation differing in no respect from formula (C) which 
I have used, save in the substitution of p—J"' for p I do not 
of course admit the correctness of this expression ; p—J' is 
certainly the elasticity of the gas when saturated with vapour 
at temperature t'. But it is the pressure of the dry gas which 
should enter into the formula, and this is p, provided p re- 
presents the height of the barometer at the time of the ex- 
periment. If this be a true view of the question, it is clear 
that Suerman's results are all a little too high, and should, in 



as deduced hy himself and Dr. Suerman. 341 

order to their being comparable with mine, be multiplied by 

P 
The apparatus employed by Suerman was one of a very 

ingenious but rather complicated description, and, as an exact 
idea of all its parts cannot be well conveyed without a dia- 
gram, for a detailed account of it I must refer to his own 
essay. The general principle, however, on which it acted is 
easily explained. Tlie air or gas which was the subject of 
experiment was, under the pressure of a column of water 
which was maintained constant by the well-known contrivance 
of Marriotte, forced from a gasometer through oil of vitriol 
contained in an adjacent Wolfe's bottle, and thence through 
a tube packed with fragments of fused chloride of calcium. 
Escaping from the tube in a state of desiccation, it was next 
made to enter one of sheet tin, through the sides of which were 
inserted a manometer, to show the interior pressure, and a 
wet and dry thermometer ; and having traversed this it passed 
on to a second gasometer, from whence it was made by the 
same means, if necessary, to return to its original reservoir, 
flowing in succession through the oil of vitriol, the chloride 
of calcium, and the calorimeter or tube containing the mano- 
meter and thermometers. In the experiments on atmospheric 
air, the pressure of water was employed ; but the other gases, 
lest they should become contaminated by the air with which 
water is naturally impregnated, were impelled through the 
apparatus by the hydrostatic pressure of a saturated solution 
of common salt, which was selected on account of the very 
small amount of air which it is capable of absorbing. From 
the sketch given of the apparatus (p. 270) the reader will have 
perceived that when the air or gas has been forced from gaso- 
meter A into gasometer B, it is possible to continue the 
current with scarcely any interruption, and cause it to return 
from B to A, passing of course in both cases in a state of 
perfect dryness through the tube containing the thermometers. 
It being, however, difficult to render the second current per- 
fectly continuous, and identical in velocity with the first, 
Suerman completed his experiment in every instance while 
the elastic fluid was passing from A to B, by resorting to the 
simple expedient of cooling the wet thermometer before its 
introduction into the apparatus, by means of which the sta- 
tionary temperature was attained long before the contents of 
gasometer A had been expelled. To this description it is only 
necessary to add, that, by the proper management of a stop- 
cock placed at the extremity of the tube containing the ther- 
mometers, he was enabled so to regulate the blast during each 



342 Prof. Apjohn on the Specific Heats of the Gases, 

experiment that the fluid stood at the same level in the two 
arms of the manometer, and that, therefore, the value of p 
was given by the height of the barometer. 

The following are, in a tabular form, some of his observa- 
tions, the pressure being converted from centimetres into 
inches, and the temperatures reduced from the centigrade 
scale to that of Fahrenheit. The number of his experiments 
with air was 12, with oxygen 9, with hydrogen 9, with car- 
bonic oxide 6, with nitrous oxide 6, and carbonic acid 8. 
But two for each gas are given here, namely, that in which t 
was a maximum, and that in which it was a minimum, for the 
several results in each series are so consistent that it would 
answer no useful purpose to quote them all. 













Sp. Heats under equal Weights. 




t 


t' 


d 


P 


(Suerman,) (J. A.) 


Atmosph. Air 1. 


74-97 


47-30 


27-17 


30-636 


•30331 
•3015 J 


-3024 


•2945 


2. 


64-27 


41-45 


22-78 


29-572 


Oxygen I. 


66-48 


42-74 


23-74 


29-811 


•27241 
-2754 / 


•2739 


-2670 


2. 


65-52 


42-57 


22-95 


30-016 


Hydrogen 1. 

2. 


64-85 
63-16 


46*11 
45-05 


18-74 
18-11 


29-619 
29-813 


6-24901 
6-1698 / 


6-2094 


6-0 189 


Carbonic Oxide 1. 


73-62 


46-68 


26-94 


29-991 


•3148 1 
-3137/ 


•3142 


•3004 


2. 


70^02 


45-16 


24-86 


30-579 


Nitrous Oxide 1. 


70^25 


46-11 


24-14 


30-017 


•21561 

•2212 J 


-2184 


-2132 


2. 


69-12 


45-95 


23-17 


30-291 


Carbonic Acid 1. 


6901 


45-05 


23-96 


29-670 


•21121 
•2194/ 


•2153 


•2087 


2. 


66-65 


44-37 


22-28 


30-170 



The numbers in the last column of preceding table, are 

f^e 30 



those which result from the formula a = 



X — , which 



4'8 ds p 

I have applied in my own researches, and they are all, it will 
be seen, less than the corresponding numbers in the preceding 
column, or those deduced by Suerman himself. 

The following table exhibits in adjacent columns the spe- 
cific heats of the respective gases under equal weights and 
equal volumes as given by Suerman, and as deduced from his 
experiments by my formula, the specific heat of air being in 
both cases represented by unity. 





Sp, Heats of equal Weights. 


Sp. Heats of equal Volumes. 


Suerman. 


J. A. 


Suerman. 


J. A. 


Air 


1-0000 

-9057 

20-5337 

1-0390 

•7222 
•7106 


1-0000 

•9066 

20-4376 

1-0200 

•7239 

•7086 


1-0000 
•9986 

1^4126 
-9722 

M005 

1-0853 


1-0000 
1-0000 
1-4061 
•9921 
M035 
1-0808 


Oxygen 

Hydrogen 


Carbonic Oxide 
Nitrous Oxide ... 
Carbonic Acid ... 



as deduced by himself and Dr. Suerman. 



343 



The accordance is here sufficient to justify the conclusion 
that the specific heats, as far at least as respects their relative 
values, are not materially affected by substituting my formula 
for that of Gay-Lussac employed by Suerman, We may 
therefore place, for the purpose of comparison, his mean re- 
sults in juxtaposition with those at which I have arrived. 





Sp. Heats of equal Volumes. 


Sp. Heats of equal Weights. [ Air = 1. 


Suerman. 


J. A. 


Suerman. 


J. A. 


Atmospheric Air 

Oxygen 

Hydrogen 

Carbonic Oxide 
Nitrous Oxide 
Carbonic Acid 


1-0000 
-9954 

1-3979 
•9923 

M229 

V0655 


1-0000 
•8080 

1^4690 
•9960 

1-1930 

1-1950 


1-0000 

•9028 

20-3191 

1-0253 

•7354 

•6975 


1-0000 

•7328 

21-2064 

1-0239 

•7827 
•7838 



A glance at this table is sufficient to show that, (oxygen 
being excepted) the numbers of Suerman and mine are almost 
identical. His number indeed for carbonic acid is somewhat 
less than mine, but the difference is quite within the limits of 
the probable errors of observation in such experiments. And 
here I may observe that M. Suerman has given an erroneous 
statement of my results, for which, however, I am myself to 
blame. During the meeting of the British Association for 
the Advancement of Science in Dublin, I laid before the che- 
mical section some experiments which I had just concluded, 
in reference to the subject under consideration, a brief account 
of which was published in the succeeding number of the re- 
ports of the Association*. The numbers given there are set 
down as the specific heats under equal weights, whereas the 
division by the specific gravities having accidentally been 
omitted, they were in reality the specific heats of equal vo- 
lumes. 

M. Suerman was aware of this omission, and has applied 
the necessary correction. The numbers, however, at which 
he has thus arrived do not still correctly represent my ex- 
periments, and for the following reason. The gases operated 
upon by me having all contained some atmospherical air, a 
correction, as has been already explained, had to be applied 
to the specific heats obtained from my hygrometric expression. 
Now the formula used for this purpose affected the correction 
upon the supposition of the numbers to which it was applied 
being the specific heats of equal weights, whereas they were 
in point of fact the specific heats of equal volumes. This cir- 

[» See Lond. and Edinb. Phil. Mag., vol. vii. p. 385.] 



844; Prof. Apjohn on the Specific Heats of the Gases, 

cumstance has been overlooked by M. Suerman, and he has 
as a consequence deduced from my experiments numbers for 
the specific heats of the different gases materially higher than 
the true. This is the chief cause of the difference between 
his numbers and mine as they appear in his thesis 6*89 ; but 
the difference in question is also partly attributable to the 
circumstance of his having had access only to my first series 
of experiments. 

The numbers then which I have obtained are 8*6, the same 
with Suerman's. This is true of them relatively but not abso- 
lutely, for his values of a for air and the different gases are 
in every instance greater than mine. This is partly owing, 
as has been already explained, to the use of the division 'p—J' 
instead of p in his formula, and to his assigning to e a higher 
value than I have given it. The chief cause, however, is that 
in his experiments the depressions were in no instance as great 
as those which I obtained; and this brings me to observe 
upon what I consider as a great defect in the apparatus which 
he employed. The tube containing the thermometers was, 
I conceive, too large, and its shape badly chosen, so that from 
both circumstances combined, it was scarcely possible that the 
air brought once in contact with the moistened bulb should 
be with certainty immediately displaced. The current in fact, 
which swept by the thermometers, being intermixed with gas 
already in the tube in a state of comparative stagnation, and 
which gas had necessarily acquired moisture from the wet ther- 
mometer, the depression indicated by the latter instrument 
was not that due to the elastic fluid in a state of perfect desic- 
cation, but the feebler one caused by gas already charged with 
a certain amount of humidity. It is very true, as Mr. Suerman 
remarks, p. 23, that the diameter of the tube containing the 
thermometers cannot be reduced beyond a certain point, for in 
such case, unless indeed the rapidity of the current be greatly 
augmented, the effect of the radiation of the sides of the tube 
upon the thermometer would become very sensible, and cause 
the instrument prematurely to reach its stationary condition. 
My objection, however, is not so much to the absolute as to 
the relative magnitude of the tube in question. It was larger 
than that of the tubes which convey the gas into and from it, 
and hence the permanent contact of a certain quantity of 
moist air with the bulb of the wet thermometer was inevitable. 
In my experiments the two thermometers were placed length- 
wise in a glass tube whose calibre was somewhat less than that 
of the other passages of the apparatus, so that the column of 
gas which it included was necessarily altogether successively 



as deduced by Jiimselfand Dr. Suerman. 345 

thrust forward, and the wet bulb thus permanently subjected 
to the action of a gaseous current in a state of perfect dry- 
ness. 

Having stated this, which I consider as the gravest objec- 
tion to which the experiments of Suerman are exposed, I shall 
next advert to, for the purpose of correcting, a couple of mis- 
takes into which he has fallen in reference to my researches 
upon the subject of specific heats. 

In the first place then Suerman, p. 81, seems to think that 
in my computations I have considered the caloric of the ela- 
sticity of vapour as an invariable quantity, whereas in point of 
fact it is the sum of it and the sensible heat of vapour whose 
value theory and experiment would seem to concur in proving 
to be constant. This is a misapprehension. In ray first paper 
on the dew-point, p. 4, will be found the following sentence: 
" In strictness the number employed (to represent c, the 
latent heat of vapour) should be 967 + 212— t, but it would 
be easy to show that the uniform use of 1129 (the value of e 
at 50°) cannot give rise to any material error." The latter 
part of this sentence was intended to apply solely to the me- 
teorological use of my formula, and not at all to it when em- 
ployed in investigating the question of gaseous specific heat. 
Dr. Suerman has fallen into this misconception from the cir- 
cumstance of his having seen only the abridged account of 
my first series of researches on this subject as published in 
the Reports of the British Association for the Promotion of 
Science. Had he however repeated the calculation of any one 
of my experiments, he would have seen that in the case of the 
specific heats I had adopted what he considers as the rigorous 
method of estimating the value of e, although I set down the 
sum of the sensible and latent heat of steam at every tempera- 
ture as somewhat less than was done by him. 

In reference to the second point, it is only necessary for 
me to recall to the attention of the reader the explanatory 
statement which I have already made. 

From the last table given above it will be seen that, if we 
except oxygen, Suerman's results and mine are almost co- 
incident. This correspondence has been noticed and admitted 
by him, as is obvious from the following passage : " Siquidem 
ad diversissimum attendamus apparatum quo usus est, faten- 
dum: satis bene illis convenire experimentaD. Apjohn atque 
nostra. Utraque vero multum distant ab experimentis De 
la Roche atque Berard, ad quae nostra propius accedunt, ra- 
tione fluidorum elasticorum elementariorum, experimenta D. 
Apjohn ratione aerum compositorum." The opinion here 
expressed cannot be considered as very well sustained by the 



346 Prof. Apjohn on the Specific Heats of the Gases, 

comparative view of our results which he gives at p. 89. 
There is in fact a material difference between his numbers 
and those which he ascribes to me ; for to confine ourselves 
to a single example, the specific heat of hydrogen compared 
to that of an equal volume of air as determined by him is 
1*3979, and, by me (as he alleges) 1-8948. But if the 
reader will refer to my first series of experiments, which alone 
were seen by Suerman previous to the publication of his 
Thesis, he will find the result for hydrogen to be 1*506, or 
but very little higher than that arrived at by the Dutch phi- 
losopher. The number therefore 1*8948 is not at all a con- 
sequence of my experiments ; but it was nevertheless, as has 
been already fully explained, very natural that it should have 
been so considered by those who had merely seen the results 
of my researches. 

The full explanation of this point has been already given, 
so that it is sufficient for me to observe here that Suerman 
was ignorant of it, and considering the numbers first published 
by me as correctly representing my experiments, was not en- 
abled to see that the general correspondence which he recog- 
nised between the results of our investigations amounted to 
an almost perfect identity. 

Having set myself right with the reader on these points, 
I have next to draw attention to some observations of Suer- 
man's of great interest and importance in relation to the prin- 
ciple of the process which both he and I have adopted in in- 
vestigating the question of the specific heats of the gases. In 
some preliminary experiments performed by him, in which 
a comparatively feeble pressure was employed, the experi- 
mental depressions were much less than those which his for- 
mula (that of Gay-Lussac) led him to expect. He therefore 
augmented the pressure, with the view of augmenting the ra- 
pidity of the current, and found that the experimental value 
o^ t — t' was thus increased. What is the cause of this? and 
is there any reason to believe that it is in our power to give 
such a degree of velocity to the current as to conduct in every 
instance not only to the maximum difference between the in- 
dications of the wet and dry thermometers, but to such dif- 
ference as may be considered to be the accurate measure of 
the specific heat or quantity which it is sought to investigate ? 

The cause of the superior influence of the augmented cur- 
rent is correctly assigned by Suerman. The caloric of ela- 
sticity of the vapour derived from the water of the wet thermo- 
meter comes chiefly from the air which impinges upon the 
moistened bulb, but partly also by radiation from the sides of 
the tube in which the instruments are placed. Now the caloric 



as deduced by himself and Dr. Suerman. 34<7 

derived from the former source necessarily augments with the 
rapidity of the gaseous current, and in a somewhat quicker 
ratio, owing to the increased depression, while the heat de- 
rived from radiation is in its amount uninfluenced by the 
speed of the blast save in as far as such speed affects the dif- 
ference between the stationary temperatures of the wet and dry 
thermometers. The relative amount therefore of the caloric 
obtained from the former source will obviously rise with the 
velocity of the current of air or gas ; and if this velocity be ren- 
dered very great, it is easy to conceive that the caloric of radia- 
tion may be a negligible quantity, and that the latent heat of 
the vapour formed may be considered without sensible error 
as exclusively derived from the aeriform fluid which is the sub- 
ject of experiment. In this latter case the depression is a maxi- 
mum, and with a quick blast it is greater than with a slow one, 
because in such case, the caloric of the vapour being derived 
in greater relative quantity from the gas, this latter must be 
cooled through a greater number of degrees in order that the 
heat which it evolves should be larger in amount. So far the 
matter is sufficiently plain, and indeed presents no difficulty 
whatever. Doubts, however, may be entertained, whether, 
with any velocity of blast which can be conveniently employed, 
the radiation of the sides of the tube can be prevented from 
exerting an appreciable influence ; and whether, with a given 
velocity of blast, the reduction of the depression due to radia- 
tion may not be different in the case of different gases. 

In reference to the first of these two points we are without 
any precise information. It is certain, as we have seen, that 
radiation must always tend to diminish the value of ^— ^', but 
the degree of its influence remains to be ascertained. In re- 
lation to the second point M. Suerman has hazarded some 
opinions, in the correctness of which I certainly cannot con- 
cur. It is well known that gases differ materially as to the 
mobility of their particles, and that this mobility follows some 
ratio reciprocal to that of the specific gravity, so that if the 
same heat be applied to equal volumes of hydrogen and car- 
bonic acid, it is propagated through the former with much 
greater velocity than through the latter. This, as is well 
known, is one of the causes which renders the method of in- 
vestigating the specific heats of gases by the velocity of heating 
incapable of yielding accurate results. Now M. Suerman ex- 
presses a strong opinion that this difference of mobility between 
the integrant molecules of different gases has an influence also 
upon the cold of evaporation. " Vix autem dubitandum vi- 
detur quin et frigus evaporationis aliquatenus hinc pendeat." 
This is to me quite unintelligible. How can the difference 



348 Prof. Apjohn on the Specific Heats of the Gases, 

of mobility in question have any influence if the gases be all 
made to move over the thermometers with the same velocity ? 
If indeed a wet thermometer were to be immersed in atmo- 
spheres of the different gases either absolutely dry, or in the 
same hygrometrical state, the depression might be expected 
to be greatest in those whose molecules were most mobile. 
But it appears to me very obvious that in the methods of ex- 
perimenting adopted by M. Suerman, as all the gases, after 
contact with the wet thermometer, are by the mechanical 
means employed removed with the same degree of speed, 
the reduction of temperature experienced by this instrument 
must in every instance be altogether independent of any pecu- 
liarity in the constitution of the respective gases, in virtue 
of which heat may be propagated through some with greater 
facility than through others. But it is not necessary to insist 
further on this point, for M. Suerman materially modifies the 
opinion previously expressed by him, as will be seen by the 
following extract from page 90 of his Thesis : " Corrigitur 
quidem pro maxima parte hie effectus aucta motus celeri- 
tate, num vero omnino ita tollatur, satis certo affirmari non 
potest." 

But there is another position of M. Suerman's which ap- 
pears to me more untenable still. In his experiments all the 
gases were driven over the thermometers with the same ve- 
locity, so that the quantities by weight which passed them 
in a given time were necessarily proportional to their specific 
gravities. Now in reference to this circumstance Suerman 
has the following passage : *' Relativus autem radiationis ex 
cylindro continenti effectus hinc pendere debet. Qui, ut 
idem esset, celeritas motus in diversis fluidis elasticis ita fuisset 
modificanda, ut, cseteris paribus, rationem inversam servaret 
ponderum specificorum." Here an influence is ascribed to mass 
which I cannot comprehend, for it is asserted that the relative 
effect of radiation is not the same for all the gases, unless the 
same ponderable amount of each passes in a given time over 
the wet thermometer. The very opposite of this proposition 
appears to me to be the truth. We have already seen that 
the ratio borne by the caloric which radiates from the sides 
of the tube to that extricated from the air cooled by contact 
with the moistened bulb, diminishes as the velocity of the 
current increases. Surely then, in order that this ratio be 
the same for the different gases, they must be all made to 
move with the same degree of speed. I do not, in fact, see 
what we have at all to do with the consideration of mass, and 
its introduction appears to me only calculated to confuse and 
mislead. 



as deduced hi) Jiimselfand Dr. Suerman. 5^9 

In my experiments, though the same degree of pressure was 
apphed to the different gases, they were driven from the one 
gasometer to the other at very different rates, hydrogen much 
quicker than nitrogen, air, or carbonic oxide, and these again 
quicker than nitrous oxide or carbonic acid. Notwithstanding, 
however, this difference of velocity, my results, as has been 
shown, are relatively the same as those of Suerman, from 
which we are entitled to infer that, provided the rate accord- 
ing to which the gases rush by the wet thermometer does 
not fall below a particular point, a variation of it does not 
sensibly affect the observed depressions. 

But it is time to terminate these remarks, and I shall do so 
with the following series of propositions : 

1. The results of Suerman are relatively the same as those 
at which I have arrived. 

2. His absolute specific heats are greater than mine, partly 
because of a difference between our formulas, and his attri- 
buting to the latent heat of aqueous vapour a higher value 
than I have done, but chiefly because the depressions obtained 
by him were uniformly less than mine. 

3. His apparatus though very ingenious was complex, and 
in consequence of the dimensions and shape of the tube con- 
taining the thermometers could not give the maximum value 
of /— ^'. My apparatus was simple, very easily operated with, 
and as it gave greater depressions must have yielded results 
closer to the truth. 

4. His apparatus was more perfect than mine in the cir- 
cumstance of its having attached to it a manometer, by which 
he was enabled to ascertain the actual pressure of the current 
of air or gas. In mine there was no such provision, but the 
augmentation of pressure was in every instance the same, and 
must also, from the manner in which the gasometers were 
connected, have been necessarily very small in amount. 

5. All results obtained by the method which we have em- 
ployed must, theoretically speaking, be higher than the true, 
as in consequence of the heat radiated from the sides of the 
containing tube upon the wet thermometer, it is prevented 
from reaching its extreme point of depression. 

6. Our researches completely refute the idea of the gases, 
whether simple or compound, having under equal volumes 
equal specific heats, and establish the very singular fact of 
hydrogen having a specific heat very nearly once and a half 
as high as that usually attributed to it. 

P.S. I should^not omit to mention that Suerman has inves- 
tigated by the same method, and by means of a very simple 
and admirable apparatus, the specific heat of atmospheric air 



350 Mr. C. T. Jackson's Chemical Afialysis of Meteoric Iron, 

at pressures Jess than those of the atmosphere. Eighteen 
experiments were performed, at pressures included between 
27'208 and 12'583 inches of mercury, and the results were 
found in very close accordance with his formula; but less 
than the numbers deducible from the theoretic expression 

fy* = c/— -) '' t given by Poisson in his Traite de Meca- 
nique, tom. ii. p. 649. 



XLVII. Chemical Analysis of Meteoric Iron, from Claiborne, 
Clarhe County, Alabama. J5j/ Charles T. Jackson. f 

Aug. 5, IVT'^' ^* ^LGER handed me this remarkable 

1834. -^ ■*■ mineral, which he had received from Mr. 
Hubbard, who had obtained the specimen during his travels 
in Alabama, and thought, from the bright streaks in it, that 
it might be an ore of silver. 

On examining this substance, it soon appeared that it was 
different from any metallic ore of terrestrial origin, and that it 
is a very peculiar and remarkable meteorite. 

Having surmised its probable origin, I was desirous of see- 
ing the gentleman who brought it from Alabama, and at the 
request of Mr. Alger, Mr. Hubbard called upon me and gave 
me the following particulars as to its locality. 

He found the specimen on the surface of the earth, near 
Lime Creek, in Claiborne, Alabama. The soil at that place 
is composed of red marl, or clay, and the rocks in place are 
sandstones, mostly of a gray colour. The mass from which 
my specimen was broken, was of an irregular triangular shape, 
rounded at the corners, and was 10 inches long by 5 or 6 
inches in thickness. It was extremely heavy, insomuch that 
he could not conveniently carry with him the whole mass, and 
therefore employed a negro to break it with a sledge-ham- 
mer; which operation proving too difficult for him, Mr. 
Hubbard took the sledge himself, and with the cutting edge, 
by many hard blows, he ultimately succeeded in detaching 
the portion in my possession. It is much to be regretted that 
he did not bring with him the whole mass, and I desired him 
to send for the remainder, but have not yet heard from him. 
He is of opinion, that there are many other similar masses 

* In this expression y is the specific heat of air under a constant press- 
ure when the height of the barometer is p, c the same when the height is 
P, and K is the ratio between the specific heat of air under a constant 
volume and a constant pressure. 

t From Silliman's American Journal of Science and Arts, vol.xxxiv. p. 332. 



from Claihorne^ Clarke County, Alabama. 351 

near the spot where this was found ; but it is not probable 
that they abound to the extent imagined. I beg leave, how- 
ever, to call tiie attention of travellers to the locality men- 
tioned, where the remainder of the specimen still exists neg- 
lected. 

Description of the Specimen. — It is of an irregular form, 
rounded upon all the sides excepting on that where it was 
fractured, which presents a rough hackly surface, with pro- 
jecting, bright, silvery streaks, and deep greenish and brown 
eroded surfaces, from which an exudation of green liquid 
takes place, on exposing the specimen to moist air. 

The rounded surface is coated with a thin layer of the sub- 
cJiloride of iron, which being removed, the mass is found to 
consist of metallic matter, resembling wrought iron, when the 
specimen is filed bright. On attempting to break off a frag- 
ment, the mass was found to be extremely tough and mal- 
leable, so as to require the aid of a file and cutting-chisel. 

Sp. gr. on three separate fragments from different parts of 
the mass, 5*750, 6*400 and 6*500. The whole mass weighs 
28 ounces avoirdupois. 

Having washed the specimen in distilled water several 
times, I tiled one side of it bright, and left it exposed to the air 
in my cabinet. In a few days, numerous grass-green drops 
of liquid began to collect on its surface, and became externally 
coated with a thin brown film. This liquid had a slight alka- 
line astringent taste, butgave noalkaline reaction with turmeric 
paper or Brazil wood solution. A few drops collected in a 
test tube and diluted with water, gave an abundant thick curdy 
"iSohite precipitate, with a solution of nitrate of silver, showing 
the presence of chlorine in combination. Ferro-cyanate of 
potash gave a blue precipitate, indicative of iron, and ammonia 
gave a precipitate o^ \he hydrated peroxide of iron. Muriate 
of ammonia having been added to a little more of the exuda- 
tion, the peroxide of iron was precipitated by ammonia, and 
the remaining liquid was of a pale blue colour, indicative of 
nickel, and on addition of pure potash, hydrate of nickel 
formed in a bulky green precipitate. 

Thus the green drops in question were proved to be com- 
posed of the hydro-chlorates of nickel and iron, and they 
doubtless form from the action of the moisture of the atmo- 
sphere upon the metallic chlorides contained in the meteorite. 

Analysis of the mass. — Several fragments of the specimen 
having been cut off by means of a steel chisel and hammer, 
their specific gravities were ascertained, and they were then 
subjected to analysis. 

Specimen 1. A fragment weighing 25 grains, sp. gr. 



352 Mr. C. T. Jackson's Chemical Analysis of Meteoric Iron, 

= 5*750, being placed in a green glass flask, and pure nitric 
acid poured upon it, no action took place until heat was ap- 
plied, when a violent effervescence, with extrication of nitrous 
acid fumes, began, and the solution was rapidly and entirely 
effected. The solution was then treated with a sufficient 
quantity of the solution of muriate of ammonia, to prevent 
the precipitation of the nickel, and then the peroxide of iron 
was thrown down by means of liquid ammonia. When the 
precipitate had subsided, the whole was thrown on a filter, 
and the peroxide of iron was thoroughly washed, dried, ig- 
nited in platina capsule, and weighed = 23'5 grs. peroxide 
of iron = 16*296 grs. metallic iron. 

The solution, which had passed the filter, was of a clear 
blue colour, with a slight amethystine tint, indicative of nickel. 
This solution and the mingled washings were evaporated in 
a glass vessel to a small bulk, and then treated, while wai'm, 
with a hot solution of pure potash, when a dense bulky green 
precipitate of the hydrate of nickel was thrown down, which 
being collected on a filter, washed, thoroughly dried and ig- 
nited in a platina crucible, weighed 8*8 grains = oxide of 
nickel = 6*927 grains metallic nickel. 

Analysis — 2d specimen. A fragment of the meteorite, 
weighing 50 grains, was found to have a sp. gr. = 6*500. 

It was placed in a green glass flask, perfectly pure nitric 
acid was poured upon it, and heat was gradually applied until 
the solution was completed. It was then diluted with pure 
distilled water, and a solution of nitrate of silver was added, 
when an abundant curdy white precipitate of chloride of silver 
took place. When the operation was complete, I filtered the 
solution, collected the washed chloride of silver, and dried 
and fused it in a small porcelain capsule. It weighed = 3 
grains = chloride of silver = 0*74 gr. chloride, or 0*76 hydro- 
chloric acid. 

The solution was then cleared of nitrate of silver, by means 
of hydro-chloric acid, and filtered. Then muriate of am- 
monia being added, the peroxide of iron was precipitated by 
pure ammonia, and after washing, drying, and ignition, 
weighed = 48 grains = 33*28 grs. metallic iron. 

The oxide of nickel was precipitated by means of a solu- 
tion of pure potash, and when collected, washed, dried, 
and ignited, weighed 15*8 grains oxide of nickel = 31*6 per 
cent. = 24*708 per cent, metallic nickel. After the separa- 
tion of the metallic oxides, the solution was treated by means 
of a solution of acetate of barytes, and a white precipitate of 
sulphate of barytes was formed, which weighed, after washing 
and drying, = 27 grains = 2 grs. sulphur. 



from Claiborne, Clarke County, Alabama. 353 

The presence of chrome and of manganese having been in- 
dicated, I took a separate portion of the meteorite, weighing 
10 grains, dissolved it in hydro-chloric acid, adding sufficient 
tartaric acid to retain the oxides in solution, neutralized the 
acid by ammonia, and precipitated the iron and nickel, by 
means of a current of hydro-sulphuric acid gas ; after filtration, 
I evaporated the solution to dryness and burned off the tar- 
taric acid in a small platina capsule under the muffle, when a 
small quantity of chromic acid was obtained, which was re- 
cognised by its characters before the blowpipe; its amount 
was estimated at 3 per cent. The manganese is also esti- 
mated. 

From the above analyses, it will appear that specimen ] st 
of the meteoric iron, having a sp. gr. of 5"750, contains in 
25 grains. 

Metallic iron 16*296 = 65-184. per cent. 

„ nickel 6-927 = 27-708 „ 

And in specimen 2nd, having a sp. gr. of 6*500 in 50 grains 
we have or in 100 grains. 

Metallic iron 33*280 66*560 

„ nickel 12*354. 24*708 

„ chrome and manganese 1*625 3*24-0 

„ sulphur 2-000 4*000 

„ chlorine '740 1-480 



49*999 99*988 

It will be remarked, that this meteorite contains an unusual 
proportion of nickel, and that the occurrence of chlorine, in 
matter of celestial origin, is here noticed for the first time. 

I beg leave therefore to invite chemists to a careful review 
of meteorites, since the occurrence of chlorine may have been 
overlooked in former analyses. 

Its occurrence in meteoric matters is a fact of great im- 
portance, in accounting for their chemical phsenomena, while 
passing through our atmosphere. 

It must also be remembered, that chloride of iron is readily 
volatilized at a high temperature, and that it is abundantly 
exhaled frorn the craters of volcanos, in various parts of our 
planet. 

Nickel, however, has not to my knowledge been discovered 
amid volcanic sublimations, but it may be worth while to call 
the attention of chemists to the subject, that it may be sought 
for in volcanic craters. 

I am however far from believing that we shall be able to 
prove that all meteorites originate from volcanic. sublimations, 

Phil. Mag. S. 3. Vol. 13. No. 83. Nov. 1838. 2 A 



S54 Chemical Analysis ofMeteon'ic Iron from Alabama. 

for there are very evidenl reasons for believing that our planet, 
statedly in its course, passes amid numerous detached masses 
of matter or asteroids, which regularly meet the earth in its 
orbit on the 13th of November; at least such are the views 
of Prof. Olmsted, of Arago and Gay-Lussac, whose opinions 
appear to be supported by the facts which they have collected. 

Allowing that meteoric matters are projected from cometary 
masses, which statedly cross the earth's orbit, coming within 
the limits of its attraction, and are subjected to the oxidizing 
influence of the atmosphere, so as to take fire and fall in 
burning masses upon the surface of the earth, we can more 
readily account for the phtenomena exhibited in their splendid 
coruscations, when we know that the meteors contain ingre- 
dients possessing remarkable decomposing powers, if brought 
into contact with water or aqueous vapour, and such are the 
effects of the chlorides of iron and nickel. 

In several instances on record, we find the meteor first 
discovering itself, bursting into fire, from the midst of a dark 
cloud, and throwing off brilliant coruscations of light, and 
ejecting ignited masses which fall to the earth ; while the 
globe of fire, from which they were thrown off, traverses the 
heavens, and gradually becomes extinct. May not therefore 
the moisture of the atmosphere have first kindled the 
meteor in its passage through the humid clouds ? I do not 
know whether they are generally too distant from the earth 
to come in contact with clouds, but from the rapidity of these 
apparent meteors they cannot be very distant, at the moment 
of their conflagration. Should chloi'ine prove to be a com- 
mon or constant ingredient, I suppose, that we should have 
a ready solution of the phsenomena involved in the problem. 

With respect to the specimen, which forms the subject of 
the present communication, if we consider its chemical com- 
position, we are forced to regard it of celestial origin ; for we 
have no similar natural alloy in this world, and it contains 
elements, which are generally found in meteoric matters, be- 
sides the new ingredient which I have discovered as one of 
its components. It is clearly impossible that this mass should 
have been factitious; for in all manufactured iron, we can 
readily detect carbon, which does not exist in our specimen, 
and the situation in which it was found is presumptive evi- 
dence that it was not manufactured, and the rocks around, 
not belonging to the class bearing metallic ores, it is impos- 
sible for it to have been derived from them, and it could not 
have been derived from the distant rocks by diluvial trans- 
portation, for no such ores exist in any of our mines. 



Mr. Faraday's Ex2)erimental Researches in Electricity. 355 

Had it been an ore of iron, reduced by a blast of lightning, 
we should not have found it alloyed with nickel. 

We are therefore led to conclude, that our specimen is 
of celestial origin, and that it is a fragment of one of those 
asteroids of cometary matter, which wandering in space, oc- 
casionally cross our orbit, and being attracted by the earth, 
so that they rush through our atmosphere, bursting into 
fire and descending, take up their abode on this sublunary 
sphere. 

Boston, May 29, 1838. 



XLVIII. Experimental Researches in Electricity. — Eleve?ith 
Series. By Michael Faraday, Esg.^ D.C.L. F.R.S, Fid- 
lei'ian Prof. Chem. Royal Institution, Corr. Memb. Royal 
and Imp. Acadd. of Sciences, Paris, Petershurgh, Florence, 
Copenhagen, Berlin, Sfc. Sj-c. 

[Continued from p. 299.] 

^ iv. Induction in curved Lines. 

1215. A MONGST those results deduced from the mole- 
■^^ cular view of induction (1166.), which, being of 
a peculiar nature, are the best tests of the truth or error of 
the theory, the expected action in curved lines is, I think, the 
most important at present; for, if shown to take place in an 
unexceptionable manner, I do not see how the old theory of 
action at a distance and in straight lines can stand, or how the 
conclusion that ordinary induction is an action of contiguous 
particles can be resisted. 

1216. There are many forms of old experiments which 
might be quoted as favourable to, and consistent with the 
view I have adopted. Such are most cases of electro- che- 
mical decomposition, electrical brushes, auras, sparks, &c. ; 
but as these might be considered equivocal evidence, inasmuch 
as they include a current and discharge, (though they have 
long been to me indications of prior molecular action (1230.)) 
I endeavoured to devise such experiments for first proofs as 
should not include transfer, but relate altogether to the pure 
simple inductive action of statical electricity. 

1217. It was also of importance to make these experiments 
in the simplest possible manner, using not more than one in- 
sulating medium or dielectric at a time, lest differences of 
slow conduction should produce effects which might errone- 
ously be supposed to result from induction in curved lines, 

2 A 2 



S56 Mr. Faraday's Researches in Electricity. {Series XL) 

It will be unnecessai'y to describe the steps of the investigation 
minutely; I will at once proceed to the simplest mode of 
proving the facts, first in air and then in other insulating 
media. 

1218. A cylinder of solid shell-lac, 0-9 of an inch in dia- 
meter and seven inches in length, was fixed upright in a 
wooden foot (fig. 3.) : it was made concave or cupped at its 
upper extremity so that a brass ball or other small arrange- 
ment could stand upon it. The upper half of the stem having 
been excited negatively by friction with warm flannel, a brass 
ball, B, 1 inch in diameter, was placed on the top, and then 
the whole arrangement examined by the carrier ball and 
Coulomb's electrometer (1180. &c.). For this purpose the 
balls of the electrometer were charged positively to about 360°, 
and then the carrier being applied to various parts of the ball 
B, the two were uninsulated whilst in contact or in position, 
then insulated*, separated, and the charge of the carrier ex- 
amined as to its nature and force. Its electricity was always 
positive, and its force at the different positions a, b, c, d, &c. 
(fig. 3. and 4.) observed in succession, was as follows : 

at « above 1000° 

b it was 149 

c 270 

d 512 

b 130 

1219. To comprehend the fijll force of these 
results, it must first be understood, that all 
the charges of the ball B and the carrier are 
charges by induction, from the action of the 
excited surface of the shell-lac cylinder; for 
whatever electricity the ball B received by 
communication from the shell-lac,either in the 
first instance or afterwards, was removed by 
the uninsulating contacts, only that due to in- 
duction remaining; and this is shown by the 
charges taken from the ball in this its uninsu- 
lated state being always positive, or of the 

contrary character to the electricity of the shell-lac. In the 
next place the charges at a, r, and d were of such a nature as 

* It can hardly be necessary for me to say here, that whatever general 
state the carrier ball acquired in any place where it was uninsulated and 
then insulated, it retained on removal from that place, notwithstanding 
that it might pass through other places, that would have given to it, if un- 
insulated, a different condition. 




Induction in curved Lines — in Air. 



357 



might be expected from an inductive action in straight lines, 
but that obtained at b is not so : it is clearly a charge by in- 
duction, but induction in a curved line-, for the carrier ball 
whilst applied to b, and after its removal to a distance of six 
inches or more from B, could not, in consequence of the size 
of B, be connected by a straight line with any part of the 
excited and inducing shell-lac. 

1220. To suppose that the upper part of the uninsulated ball 
B, should in some way be retained in an electrified state by that 
portion of the surface which is in sight of the 
shell-lac, would be in opposition to what we know 
already of the subject. Electricity is retained 
upon the surface of conductors only by induction 
(1178.); and though some persons may not 
be prepared as yet to admit this with respect 
to insulated conductors, all will as regards 
uninsulated conductors like the ball B; and 
to decide the matter we have only to place the 
carrier ball at e (fig. 4.), so that it shall not 
come in contact with B, uninsulate it by a 
metallic rod descending perpendicularly, in- 
sulate it, remove it, and examine its state: it 
will be found charged with the same kind of 
electricity as, and even to a higher degree 
(1224'.) than, if it had been in contact with 
ofB. 

1221. To suppose, again, that induction acts in some way 
through or across the metal of the ball, is "" 
negatived by the simplest considerations ; 
but a fact in proof will be better. If in- 
stead of the ball B a small disc of metal 
be used, the carrier may be charged at, or 
above the middle of its upper surface ; but 
if the plate be enlarged to about li or 2 
inches in diameter, C (fig. 5.), then no 
charge will be given to the carrier atj^ 
though when applied nearer to the edge at 
g, or even above the middle at /z, a charge 
will be obtained ; and this is true though 
the plate may be a mere thin film of gold- 
leaf. Hence it is clear that the induction 

is not through the metal, but through the air or dielectric, 
and that in curved lines. 

1222. I had another arrangement, in which a wire passiu'i- 
downwards through the middle of the shell-lac cylinder to the 
earth, was connected with the ball B (fig. 6.) so* as to keep it 




summit 



Fig 5. 
® 





358 Mr. Faraday's Researches in Electricity. {Series XL) 

in a constantly uninsulated state. This was a very Fig. 6. 
convenient form of apparatus, and the results with 
it were the same as those described. 

1223. In another case the ball B was supported 
by a shell-lac stem, independently of the excited 
cylinder of shell-lac, and at half an inch distance 
from it ; but the effects were the same. Then the 
brass ball of a charged Leyden jar was used in 
place of the excited shell-lac to produce induc- 
tion ; but this caused no alteration of the phaeno- 
mena. Both positive and negative inducing charges 
were tried with the same general results. Finally, 
the arrangement was inverted in the air for the 
purpose of removing every possible objection to 
the conclusions, but they came out exactly the same. 

1224. Some results obtained with a brass hemisphere in- 
stead of the ball B were exceedingly interesting. It was 1*36 
of an inch in diameter, (fig. 7.), and being 
placed on the top of the excited shell-lac cy- 
linder, the carrier ball was applied, as in the 
former experiments (1218.), at the respective 
positions delineated in the figure. At / the 
force was 112°, at k 108°, at / 65°, at m 35° ; 
the inductive force gradually diminishing, as 
might have been expected, to this point. 
But on raising the carrier to the position n 
the charge increased to 87°; and on raising 
it still higher to o, the charge still further 
increased to 105°: at a higher point still, p, 
the charge taken was smaller in amount, being 
98°, and continued to diminish for more 
elevated positions. Here the induction fairly 
turned a corner. Nothing, in fact, can better 

show both the curved lines or courses of the inductive action, 
disturbed as they are from their rectilineal form by the shape, 
position, and condition of the metallic hemisphere; and also 
a lateral tension, so to speak, of these lines on one another : 
all depending, as I conceive, on induction being an action of 
the contiguous particles of the dielectric thrown into a state of 
polarity and tension, and mutually related by their forces in 
all directions. 

1225. As another proof that the whole of these actions 
were inductive, I may state a result which was exactly what 
might be expected, namely, that if uninsulated conducting 
matter was brought round and near to the excited shell-lac 
stem, then the inductive force was directed towards it, and 




Induction in curved Lines — in Fluids^ Solids. 359 

could not be found on the top of the hemisphere. Removing 
this matter the hnes of force resumed their former direction. 
The experiment affords proofs of the lateral tension of these 
lines, and supplies a warning to remove such matter in re- 
peating the above investigation. 

1226. After these results on curved inductive action in air 
I extended the experiments to other gases, using first carbonic 
acid and then hydrogen : the phaenomena were precisely 
those already described. In these experiments I found that 
if the gases were confined in vessels they required to be very 
large, for whether of glass or earthenware, the conducting 
power of such materials is so great that the induction of the 
excited shell-lac cylinder towards them is as much is if they 
were metal ; and if the vessels be small, so great a portion of 
the inductive force is determined towards them that the lateral 
tension or mutual repulsion of the lines of force before spoken 
of, (1224.) by which their inflexion is caused, is so much re- 
lieved in other directions, that no inductive charge will be 
given to the carrier ball in the positions A-, I, m, n, o^p, (fig. 7.). 
A very good mode of making the experiment is to let large 
currents of the gases ascend or descend through the air, and 
carry on the experiments in these currents. 

1227. These experiments were then varied by the substitu- 
tion of a liquid dielectric, namely, oil of turipentine^ in place 
of air and gases. A dish of thin glass well covered with a 
film of shell-lac, (1272.) and found by trial to insulate well, 
had some highly rectified oil of turpentine put into it to the 
depth of half an inch, and being then placed upon the top of 
the brass hemisphere, (fig. 7.) observations were made with 
the carrier ball as before (1224.). The results were the same, 
and the circumstance of some of the positions being within 
the fluid and some without, made no sensible difference. 

1228. Lastly, I used a few solid dielectrics for the same 
purpose, and with the same results. These were shell-lac, 
sulphur, fused and cast borate of lead, flint glass well covered 
with a film of lac, and spermaceti. The following was the 
form of experiment with sulphur, and all were of the same 
kind. A square plate of the substance, two inches in extent 
and 0*6 of an inch in thickness, was cast with a small hole or 
depression in the middle of one surface to receive the carrier 
ball. This was placed upon the surface of the metal hemi- 
sphere (fig. 9.) arranged on the excited lac as in former cases, 
and observations wei"e made at w, o, /?, and q. Great care 
was required in these experiments to free the sulphur or other 
solid substance from any charge it might previously have 
received. This was done by breathing and wiping (1203.), 



360 Mr. Faraday's Researches in Eledricitij, [Series XL) 



■ jg- 9- 



and the substance being tbiuid free from 
all electrical excitement, was then used 
in the experiment ; after which it was 
removed and again examined, to ascer- 
tain that it had received no charge, but 
had acted really as a dielectric. With 
all these precautions the results were the 
same : and it is thus very satisfactory 
to obtain the curved inductive action 
through solid bodies^ as any possible 
effect from the translation of charged 
particles in fluids or gases, which some 
persons might imagine to be the case, is 
here entirely negatived. 

1229. In these experiments with solid 
dielectrics, the degree of charge, as- 
sumed by the carrier ball at the situations w, o, p (fig. 9.), 
was decidedly greater than that given to the ball at the same 
places when air only intervened between it and the metal 
hemisphere. This effect is consistent with what will hereafter 
be found to be the respective relations of these bodies, as to 
their power of facilitating induction through them (1269. 
1273. 1277.). 

1230. I might quote many other forms of experiment, some 
old and some new, in which induction in curved or contorted 
lines takes place, but think it unnecessary after the preceding 
results; I shall therefore mention but two. If a conductor 
A, (fig. 8.) be electrified, and an uninsulated metallic ball B, 

Fig. 8. 





or even a plate, provided the edges be not too thin, be held 
before it, a small electrometer at c or at d, uninsulated, will 
give signs of electricity, opposite in its nature to that of A, 
and therefore caused by induction, although the influencing 
and influenced bodies cannot be joined by a right line passing 
through the air. Or if, the electrometers being removed^ a 
point be fixed at the back of the ball in its uninsulated state 
as at C, this point will become luminous and discharge the 
conductor A. The latter experiment is described by Nichol- 
son*, who, however, reasons eri'oneously upon it. As to its 

* Encyclopcedia Brilannica, vol. vi. p. 504. 



Inductioti in curved Lines- — in Fluids, Solids. 361 

introduction here, though it is a case of discharge, the dis- 
charge is preceded by induction, and that induction must be 
in curved lines. 

1231. As argument against the received theory of induc- 
tion and in favour of that whicli I have ventured to put forth, 
I cannot see how the preceding results can be avoided. The 
effects are clearly inductive effects produced by electricity, 
not in currents but in its statical state, and this induction is 
exerted in lines of force which, though in many experiments 
they may be straight, are here curved more or less according 
to circumstances. 1 use the term line of inductive force merely 
as a temporary conventional mode of expressing the direction 
of the power in cases of induction ; and in the experiments with 
the hemisphere (1224.), it is curious to see how, when certain 
lines have terminated on the under surface and edge of the 
metal, those which were before lateral to them expand and open 
out from each other, some bending round and terminating their 
action on the upper surface of the hemisphere, and others 
meeting, as it were, above in their progress outwards, uniting 
their forces to give an increased charge in the carrier ball, at 
an increased distance from the source of power, and influencing 
each other so as to cause a second flexure in the contrary di- 
rection from the first one. All this appears to me to prove 
that the whole action is one of contiguous particles, related to 
each other, not merely in the lines which they may be con- 
ceived to form through the dielectric, between the inductric 
and the inducteous surfaces, but in other lateral directions 
also. It is this which gives the effect equivalent to lateral re- 
pulsion or expansion in the lines of force I have spoken of, and 
enables induction to turn a corner (1304.). The power, in- 
stead of being like that of gravity, which relates particles 
together through straight lines, whatever other particles may 
be between them, is more analogous to that of a series of 
magnetic needles, or to the condition of the particles consi- 
dered as forming the whole of a straight or a curved mag- 
net. So that in whatever way I view it, and with great 
suspicion of the influence of favourite notions over myself, I 
cannot perceive how the ordinary theory of induction can be 
a correct representation of that great natural principle of 
electrical action. 

1232. I have had occasion in describing the precautions 
necessary in the use of the inductive apparatus, to refer to 
one founded on induction in curved lines (1203.); and after 
the expei'iments already described, it will easily be seen how 
great an influence the shell-lac stem may exert upon the 



362 Mr. Faraday's Researches in Electricity. {Series XL) 

charge of the carrier ball when applied to the apparatus 
(1218.), unless that precaution be attended to. 

1233. I think it expedient, next in the course of these ex- 
perimental researches, to describe some effects due to con- 
duction, obtained with such bodies as glass, lac, sulphur, &c., 
which had not been anticipated. Being understood, they will 
make us acquainted with certain precautions necessary in in- 
vestigating the great question of specific inductive capacity. 

1234. One of the inductive apparatus already described 
(1187, &c.) had a hemispherical cup of shell-lac introduced, 
which being in the interval between the inner ball and the 
lower hemisphere, nearly occupied the space there; conse- 
quently when the apparatus was charged, the lac was the di- 
electric or insulating medium through which the induction 
took place in that part. When this apparatus was first charged 
with electricity (1198.) up to a certain intensity, as 400°, 
measured by the Coulomb's electrometer (1180.), it sank 
much faster from that degree than if it had been previously 
charged to a higher point, and had gradually fallen to 400° ; 
or than it would do if the charge were, by a second applica- 
tion, raised up again to 400°; all other things remaining the 
same. Again, if after having been charged for some time, as 
fifteen or twenty minutes, it was suddenly and perfectly dis- 
charged, even the stem having all electricity removed from it 
(1203.), then the apparatus being left to itself, would gra- 
dually recover a charge, which in nine or ten minutes would 
rise up to 50° or 60°, and in one instance to 80^. 

1235. The electricity which in these cases returned from 
an apparently latent to a sensible state, was always of the 
same kind as that which had been given by the charge. The 
return took place at both the inducing surfaces ; for if after the 
perfect discharge of the apparatus the whole was insulated, 
as the inner ball resumed a positive state the outer sphere ac- 
quired a negative condition. 

1236. This effect was at once distinguished from that pro- 
duced by the excited stem acting in curved lines of induction 
(1203. 1232.), by the circumstance that all the returned elec- 
tricity could be perfectly and instantly dischai'ged. It ap- 
peared to depend upon the shell-lac within, and to be, in 
some way, due to electricity evolved from it in consequence of 
a previous condition into which it had been brought by the 
charge of the metallic coatings or balls. 

1237. To examine this state more accurately, the appa- 
ratus, with the hemispherical cup of shell-lac in it, was charged 
for about forty-five minutes to above 600^ with positive elec- 



Induction Apparatus — Effects of Conduction in it. 363 

tricity at the balls h and B (fig. 1.) above and within. It was 
then discharged, opened, the shell-lac taken out, and its state 
examined; this was done by bringing the carrier ball near 
the shell-lac, uninsulating it, insulating it, and then observing 
what charge it had acquired. As it would be a charge by 
induction, the state of the ball would indicate the opposite 
state of electricity in that surface of the shell- lac which had 
produced it. At first the lac appeared quite free from any 
charge; but gradually its two surfaces assumed opposite states 
of electricity, the concave surface, which had been next the 
inner and positive ball, assuming a positive state, and the 
convex surface, which been in contact with the negative coat- 
ing, acquiring a negative state; these states gradually increa- 
sing in intensity for some time. 

1238. As the return action was evidently greatest instantly 
after the discharge, I again put the apparatus together, and 
charged it for fifteen minutes as before, the inner ball posi- 
tively. I then discharged it, instantly removing the upper 
hemisphere with the interior ball, and, leaving the shell- 
lac cup in the lower uninsulated hemisphere, examined its 
inner surface by the carrier ball as before (1237-)* In this 
way I found the surface of the shell-lac actually negative, or 
in the reverse state to the ball which had been in it ; this state 
quickly disappeared, and was succeeded by a positive condi- 
tion, gradually increasing in intensity for some time, in the 
same manner as before. This first negative condition of the 
surface opposite the positive charging ball is a natural con- 
sequence of the state of things, the charging ball being in 
contact with the shell-lac only in a few points. It does not 
interfere with the general result and peculiar state now under 
consideration, except that it assists in illustrating in a very 
marked manner the ultimate assumption by the surfaces of 
the shell-lac of an electrified condition, similar to that of the 
metallic surfaces opposed to or against them. 

1239. Glass was then examined with respect to its power 
of assuming this peculiar state. I had a thick flint glass 
hemispherical cup formed, which would fit easily into the 
space o of the lower hemisphere (1188. 1189.); it had been 
heated and varnished with a solution of shell-lac in alcohol, 
for the purpose of destroying the conducting power of the 
vitreous surface. Being then well warmed and experimented 
with, I found it could also assume the same state^ but not ap- 
parently to the same degree, the return action amounting in 
different cases to quantities from 6° to 18°. 

1240. Spermaceti experimented with in the same manner 
gave striking results. When the original charge had been 



364? Mr. Faraday's Researches in Electricity. (Series XI.) 

sustained for fifteen or twenty minutes at about 500°, the re- 
turn charge was equal to 95° or 100°, and was about fourteen 
minutes arriving at the maximum effect. A charge continued 
for not more than two or three seconds was here succeeded by 
a return charge of 50° or 60°. The observations formerly 
made (1234.) held good with this substance. Spermaceti, 
though it will insulate a low charge for some time, is a better 
conductor than shell-lac, glass, and sulphur; and this con- 
ducting power is connected with its readiness in exhibiting 
the particular effect under consideration. 

1241. Sulphur. — I was anxious to obtain the amount of 
effect with this substance, first, because it is an excellent in- 
sulator, and in that respect would illustrate the relation of the 
effect to the degree of conducting power possessed by the di- 
electric (1247.); and in the next place, that 1 might obtain 
that body giving the smallest degi'ee of the effect now under 
consideration, for the investigation of the question of specific 
inductive capacity (1277.). 

1242. With a good hemispherical cup of sulphur cast solid 
and sound, I obtained the return charge, but only to an 
amount of 17° or 18°. Thus glass and sulphur, which are 
bodily very bad conductors of electricity, and indeed almost 
perfect insulators, gave very little of this return charge. 

1243. I tried the same experiment having air only in the 
inductive apparatus. After a continued high charge for some 
time I could obtain a little effect of return action, but it was 
ultimately traced to the shell-lac of the stem. 

1244. I sought to produce something like this state with one 
electric power and without induction ; for upon the theory 
of an electric fluid or fluids, that did not seem impossible, 
and then I should have obtained an absolute charge (1169. 
1177.), or something equivalent to it. In this I could not 
succeed. 1 excited the outside of a cylinder of shell-lac very 
highly for some time, and then quickly discharging it (1203.), 
waited and watched whether any return charge would appear, 
but such was not the case. This is another fact in favour of 
the inseparability of the two electric forces, and another argu- 
ment for the view that induction and its concomitant phaeno- 
mena depend upon a polarity of the particles of matter. 

1245. Although inclined at first to refer these effects to a 
peculiar masked condition of a certain portion of the forces, 
I think I have since correctly traced them to known prin- 
ciples of electrical action. The effects ap})ear to be due to 
an actual penetration of the charge to some distance within 
the electric, at each of its two surfaces, by what we call con- 
duction; so that, to use the ordinary phrase, the electric 



dielec 




Induction Apparatus— Effects of Condtiction in it. 365 

forces sustaining the induction are not upon the metallic sur- 
faces only, but upon and within the dielectric also, extending 
to a greater or smaller depth fi-om the metal linings. Let c 
(fig. 10.) be the section of a plate of any dielectric, a and b 
being the metallic coatings; let 6 be uninsulated, 
and a be charged positively; after ten or fiitteen Fig. 10. 
minutes, if a and b be discharged, insulated, and ^ 

immediately examined, no electricity will appear 
in them ; but in a short time, upon a second ex- 
amination, they will appear charged in the same 
way, though not to the same degree, as they were 
at first. Now suppose that a portion of the po- 
sitive force has, under the coercing influence of 
all the forces concerned, penetrated 
trie and taken up its place at 
the line j), a corresponding 
portion of the negative force 
having also assumed its posi- 
tion at the line n ; that in fact the electric at these two parts 
has become charged positive and negative ; then it is clear 
that the induction of these two forces will be much greater 
one towards the other, and less in an external direction, now 
that they are at the small distance np from each other, than 
when they were at the larger interval a b. Then let a and b 
be discharged; the discharge destroys or neutralizes all ex- 
ternal induction, and the coatings are therefore found by the 
carrier ball unelectrified ; but it also removes almost the whole 
of the forces by which the electric charge was driven into the 
dielectric, and though probably a part goes forward in its 
passage and terminates in what we call discharge, the greater 
portion returns on its course to the surfaces of c, and conse- 
quently to the conductors a and b, and constitutes the re- 
charge observed. 

124:6. The following is the experiment on which I rest for 
the truth of this view. Two plates of spermaceti, d andy 
(fig. 11.), were put together to form the dielectric, a and b 
being the metallic coatings of this compound plate, as before. 
The system was charged, then discharged, insulated, ex- 
amined, and found to give no indications of electricity to the 
carrier ball. The plates d andy were then separated from 
each other, and instantly a with d was found in a positive state, 
and b with y in a negative state, nearly all the electricity 
being in the linings a and b. Hence it is clear that, of the 
forces sought for, the positive was in one half of the com- 
pound plate and the negative in the other half; for when re- 
moved bodily with the plates from each other's inductive in- 



366 Mr. Faraday's Researches in Electricity. {Series XL) 

fluence, they appeared in separate places, and resumed of 
necessity their power of acting by induction on the electricity 
of surrounding bodies. Had the effect depended upon a pe- 
culiar relation of the contiguous particles of matter only, then 
each half plate, d and^ should have shown positive force on 
one surface and negative on the other. 

1247. Thus it would appear that the best solid insulators, 
such as shell-lac, glass, and sulphur, have conductive pro- 
perties to such an extent, that electricity can penetrate them 
bodily, though always subject to the overruling condition of 
induction (1 1 78.). As to the depth to which the forces pene- 
trate in this form of charge of the particles, theoretically, it 
should be throughout the mass, for what the charge of the 
metal does for the portion of dielectric next to it, should be 
done by the charged dielectric for the portion next beyond it 
again ; but probably in the best insulators the sensible charge 
is to a very small depth only in the dielectric, for otherwise 
more would disappear in the first instance whilst the original 
charge is sustained, less time would be required for the as- 
sumption of the particular state, and more electricity would 
re-appear as return charge. 

1248. The condition of time required for this penetration 
of the charge is important, both as respects the general re- 
lation of the cases to conduction, and also the removal of an 
objection that might otherwise properly be raised to certain 
results respecting specific inductive capacities, hereafter to be 
given (1269. 1277.). 

1249. It is the assumption for a time of this charged state 
of the glass between the coatings in the Leyden jar, which 
gives origin to a well-known phaenomenon, usually referred to 
the diffusion of electricity over the uncoated portion of the 
glass, namely, the residual charge. The extent of charge 
which can spontaneously be recovered by a large battery, after 
perfect uninsulation of both surfaces, is very considerable, and 
by far the largest portion of this is due to the return of elec- 
tricity in the manner described. A plate of shell-lac six 
inches square, and half an inch thick, or a similar plate of 
spermaceti an inch thick, being coated on the sides with tin- 
foil as a Leyden arrangement, will show this effect exceed- 
ingly well. 

1250. The peculiar condition of dielectrics which has now 
been described, is evidently capable of producing an effect 
interfering with the results and conclusions drawn from the use 
of the two inductive apparatus, when shell-lac, glass, &c. are 
used in one or both of them (1192. 1207.); for upon dividing 
the charge in such cases according to the method described 



Justification of the Contact Theory of Galvanism, 367 

(1198. 1207.)» it is evident that the one just receiving? its half 
charge must fall faster in its tension than the other. For sup- 
pose app. i. first charged, and app. ii. used to divide with it; 
though both may actually lose alike, yet app. i., which has 
been diminished one half^ will be sustained by a certain de- 
gree of return action or charge (1234.), whilst app. ii. will 
sink the more rapidly from the coming on of the particular 
state. I have endeavoured to avoid this interference by per- 
forming the whole process of comparison as quickly as pos- 
sible, and taking the force of app. ii. immediately after the di- 
vision, before any sensible diminution of the tension arising 
from the assumption of the peculiar state could be produced ; 
and I have assumed that as about three minutes pass between 
the first charge of app. i. and the division, and three minutes 
between the division and discharge, when the force of the 
non-transferable electricity is measured, the contrary ten- 
dencies for those periods would keep that apparatus in a mo- 
derately steady and uniform condition for the latter portion 
of time. 

1251. The particular action described occurs in the shell- 
lac of the stems, as well as in the dielectric used within the 
apparatus. It therefore constitutes a cause by which the out- 
side of the stems may in some operations become charged 
with electricity, independent of the action of dust or carrying 
particles (1203.). 

[To be continued.] 



XLIX. Justification of the Contact Theory of Galvanism. 
By G. Th. Fechner. 

[Continued from p. 21 7-] 

II. Facts 'which relate to the closed circuit. 

1. TT appears according to the theory of contact as if iron, 
■"^ which when brought into contact with copper in water 
or diluted acids exhibits positive electricity, must on the con- 
trary be positive in all other fluids ; it acts however, never- 
theless, negatively in a solution of sulphuret of potassium 
[Sch'iscefelleber). Other examples may be placed by the side 
of this, in which also the electromotive condition of the metals 
changes with the consistence of the intermediate fluid, for in- 
stance, that of tin and copper is in solution of ammonia the 
reverse of what it is in pure water, and that of copper and 
lead, in concentrated nitric acid, is the opposite of that in di- 
luted nitric acid, which immediately obviates the objection, 



368 G. Th. Fechner's Justification of the 

that the different electromotive action of the various fluids 
upon the metals should call forth of itself an apparent reversion 
of the polarity, since in the latter experiment the fluid, disre- 
garding the degree of concentration, remains the same. Ac- 
cording to the chemical view all these cases are easily ex- 
plained by the general rule, that that metal which is most 
strongly acted upon by the fluid, is always the positive one 
(De la Rive in h\s, RechercheSi p. 7.)« 

To this objection I believe I have paid sufficient attention 
in a detailed memoir respecting the reversions of polarity of 
the circuit*, and with which undoubtedly De la Rive cannot 
be acquainted. I have shown that when copper in a solu- 
tion of sulphuret of potassium is positive with respect to 
iron, this is caused by a change (perceptible even to the eye) 
of its surface, which takes place immediately on immersion in 
a concentrated, gradually on immersion in a diluted solution 
of sulphuret of potassium, whence therefore in a diluted so- 
lution the normal divergence also first takes place, and then 
gradually passes over into the opposed. Besides, the copper, 
changed in the solution of sulphuret of potassium, is even 
positive towards iron in other fluids. I have further proved 
that even in other concentrated fluids and with other metals, 
in which an electromotive state opposed to the general one 
may be observed, in general there exists a certain degree of 
dilution of the fluid, below which the metals indicate at the 
beginning the normal state, which then gradually passes over 
into the opposite (if the solution be not too dilute), which also 
argues a change gradually produced in the surfacesof the metals, 
although it cannot in every case be demonstrated in a direct 
manner. 1 have also shown by other different experiments that 
in these cases the change of the fluid has no influence on the 
effects. If, moreover, the positive metal happens to be the one 
which is also alwiiys acted upon most strongly, then this coinci- 
dence of the two circumstances would in no degree determine 
which of the two was to be considered as the cause of the other ; 
as, however, the cases given in my memoir did not include 
those specifically related by De la Rive of the reverse action of 
tin and copper in ammonia and of lead and copper in concen- 
trated nitric acid, I have lately convinced myself that in fact, 
if we unite tin and copper in officinal liquor ammonice, lead and 
copper in concentrated nitric acid, even when these liquids are 
not diluted, the divergence in the beginning indicates the 
normal positive condition respectively of the tin and the lead, 
which however after a short time (accordingly as the change 

* Schweigger's Journal, vol. liii. p. 61 — 129, or Biot's Lchrbuch (Precis) 
vol. iii. p. 93. 



Contact Theory of Galvanism. ^69 

takes place in the metals) passes over into the negative. The 
taking place of the change of the metals in these fluids may 
also be proved by various other experiments, which however 
I here omit as they may be brought forward in connexion 
much better in another place. 

The changes which fluids produce in metals have certainly 
not been sufficiently attended to and studied, and I shall often 
have occasion in this memoir to return to this point. All the 
experiments which Pfaff^ Karsten, Becquerel, and others have 
made on the production of electricity between fluid and solid 
bodies are at least complicated by these changes and demand 
in this respect a revision. It is not at all impossible that the 
result of these experiments depends entirely on such changes. 
Further experiments will, I hope, soon solve this part of the 
question. 

2. Schoenbein has published in these Annalen (vol. xxxix. 
p. 351*.) an experiment which he considers to be especially 
decisive in favour of the chemical theory, and which chiefly 
amounts to this, that an iron wire rendered passive by pre- 
vious immersion in nitric acid, then connected with the circuit 
in a solution of sulphate of copper by means of a platinum 
wire, precipitates no copper and produces no current, but 
that a current immediately takes place if by any cause the 
passive condition of the wire is destroyed, i. e. if its chemical 
state is again restored. 

With respect to this experiment we may state the fol- 
lowing : 

By previous experiments performed by Wetzlar, and lately 
by myself, it has been sufficiently shown that the change (as 
little explained in the sense of the chemical theory as in that 
of the contact theory) which iron undergoes in nitric acid 
and in a solution of concentrated nitrate of silver, renders it 
considerably more negative than previously. That a highly 
negative metal neither precipitates copper, nor gives with 
platinum any perceptible current, (especially if the metals are 
employed in the form of wire, and a multiplier is made use of, 
of little sensibility,) certainly cannot be regarded as incompa- 
tible with the theory of contact, and as little, that a current 
immediately re-appears with the precipitation of the copper, 
if by any cause that change of surface has been destroyed. 
Where is the proof that the precipitation of the copper is not 
rather the consequence than the cause of the restored electri- 
cal action ? Besides, it is possible that the peculiar change 
which iron undergoes in nitric acid may also increase its 

[* See also L. and E. Phil. Mag., vol. x. p. 275; and also p. 167 of the 
present volume.] 
Phil. Mas. S. 3. Vol. 13. No. 83. Nov. 1838. 2 B 



370 G. Th. Fecliner's Justification of the 

power of opposing the transfer of electricity. (Compare with 
No. 3.) I cannot find the least proof in this experiment. From 
the same point of view we must also consider the experiment 
published byDe la Rive in these Annalen^lxoi. xl. p. 368. If 
I say that iron also undergoes a change of the same kind in 
caustic potash, that it becomes considerably more negative by 
its action than before, all that is there stated appears to me 
explained, although the change of the iron itself may still 
need an explanation not less when regarded according to the 
chemical theory than to the theory of contact. Among other 
circumstances, we find a proof of this change, that iron con- 
nected with copper in caustic potash to form a circuit, at first 
gives the normal divergence of the multiplier, which diver- 
gence makes the iron appear positive, but shortly after it 
changes. That, however, iron gives no current with platinum 
in caustic potash 1 did not find to be the case. On apply- 
ing a very delicate multiplier the current was strong enough 
to place the double needle almost perpendicular to the 
coils. 

3. The following experiments belong to those which at first 
sight appear most strikingly to favour the chemical theory, 
and to which its supporters attach especial importance. Zinc 
with copper gives in distilled water, as also in concentrated 
sulphuric acid, closed, only weak electric currents ; in diluted 
sulphuric acid, a mixture of both fluids, very powerful ones. 
Since it is not probable that the proper conducting power of 
the fluids is changed by their mixture, there remains nothing 
more than to attribute the increased current to the increased 
chemical action which takes place on diluting the sulphuric 
acid, which produces the increased development of electricity. 
Similar to this is the Ibllowing experiment: platinum with 
gold gives in pure nitric acid, as also in pure muriatic acid, 
a weak and transient, according to De la Rive's statement, an 
imperceptible current, but in aqua regia an apparently strong 
one. Many similar examples are mentioned which all belong 
to the same class. However, supposing that the mixture of 
the fluids does not change their conducting power *, it is still 
questionable whether the increased effect in all these cases 
produced by increased chemical action does not depend merely 
on this, that the opposition to the transfer decreases with die 
increase of chemical action. In fact I have shown in my gal- 
vanic measurements that this opposition is smaller in power- 

[* It appears to us, on the contrary, that the chemical action which 
ensues on the mixture of the nitric and muriatic acids, hy which they are 
both, in part, decomposed, must effect a corresponding change in their 
conducting power. — Edit.] 



Contact Theory ofGalvanhm. 371 

fully acting fluids. The following experiments will probably 
be more decisive with respect to the subject now before us. 

If I bring a fluid between homogeneous plates, a current 
ought not to originate according to any theory, on connecting 
the plates with the multiplier, from the independent action of 
this system; or if 1 2 n/^r/)o<,f a fluid between homogeneous plates 
in an active circuit, this interposition would, according to each 
theory, influence the force of the circuit in no other manner 
than by its opposing power as long as the plates are un- 
changed^. It then appears : — 

a. That concentrated sulphuric acid inserted in an active 
circuit between homogeneous zinc plates or muriatic acid 
between homogeneous platinum plates, considerably weakens 
the force of this circuit; a proof that a strong opposition to 
the conduction has arisen in the circuit. 

h. That in like manner distilled water inserted in the cir- 
cuit between homogeneous zinc plates or nitric acid between 
homogeneous platinum plates considerably diminishes its 
power. 

c. That, however, diluted sulphuric acid inserted in the cir- 
cuit between homogeneous zinc plates, or a mixture of mu- 
riatic and nitric acids between homogeneous platinum plates, 
weaken the power but little in proportion ; a proof that from 
the mixture (and that undoubtedly from the excited chemical 
reaction) of the fluids the opposition to the conduction has 
really diminished. The details of the experiments are as 
follows. 



In the apparatus A a zinc and copper circuit K Z (of each 
plate 1 1 '2 Parisian square inches immersed at 4 lines distance) 
was connected in highly acidulated water with the multiplier 
M (consisting of thick copper wire but not of many coils), and 
the interposed intermediate apparatus which contained the 
zinc plates a a, and either water or fuming sulphuric acid, or 
diluted sulphuric acid, as the exciting fluid. The distance of 
the plates a a was 14 lines, the immersed surface Tl square 
inch. The measure of the power of the current was always 
taken by the first oscillations of the needle, which was placed 

2 B 2 



372 G. Th. Fechner's Justification of the 

perpendicular to the coils, immediately after the closing, by 
means of the method already sufficiently described elsewhere ; 
and the circuit, immediately I'e-opened in order to avoid as 
much as possible the decrease of action. Moreover, before 
each new measurement the active condition of the zinc and 
copper circuit was not only restored by being kept long out, 
(vide on this subject my measurements of the galvanic cir- 
cuit,) but even the zinc plates a a, were cleaned by filing. 
If the power of the current without the interposed apparatus 
was represented by 1000, it became on the insertion of the 
intermediate apparatus : 

When the interposed apparatus was filled withl Q.QonK 

distilled water J 

with fuming sulphuric acid . . 64-685 

with diluted sulphuric acid . , 851*04- 

The last power could not be accurately measured on account 
of the extreme velocity of the first oscillations, and probably 
approaches much closer to the power without the interposed 
apparatus than as stated. 

For the preparation of the dilute sulphuric acid I took, by 
estimation, 1 volume of fuming sulphuric acid and 3 volumes 
of distilled water. 

On employing platinum instead of zinc plates in the inter- 
posed apparatus, 1 obtained the following relative current 
forces according to the fluids it was charged with, by which, 
the value of the current without the interposed apparatus 
being again fixed at = 1000, 

When the apparatus was filled with concen-1 17-703 

trated nitric acid J 

with muriatic acid .... 2*5822 

with nitro-muriatic acid . . 338*34 

The nitro-muriatic acid was composed of about equal vo- 
lumes of each acid (I did not however take the sp. gr.). It 
is remarkable that the action in the nitro-muriatic acid did 
not immediately after closing the circuit attain the assigned 
magnitude, but was considerably weaker, but very quickly 
rose to that magnitude, which circumstance I frequently ob- 
served; while, in the experiment with zinc, sulphuric acid and 
water, the power here stated was attained immediately. The 
change, on which this increase depended, was an action of 
the closure itself, since it was even indicated when the pla- 
tinum plate had already stood for some time in nitric acid 
previously to the closing, and was repeated at new closings 
after intervening breaks. In the mean time it cannot be 
ascribed to a gradual charging of the plate so far as by that 
is understood a change of the electro-motive power, since by 



Contact Theory of Galvanism. 373 

this the force of the circuit would only have decreased ; for 
the platinum plate communicating metallically with the cop- 
per, indicated itself, not only by a development of gas bub- 
bles in the circuit, but even by a distinct experiment, the 
circuit being made with it after some lapse of time between 
the closings, as negative with relation to the copper. The 
cause then of the gradually increasing action could only be 
sought for in the decrease of opposition gradually taking place. 

The experiment with the zinc plates was performed twice, 
that with the platinum plates three times, on different days, with 
results exactly corresponding. Moreover De la Rive affirms 
that platinum connected in pure nitric acid with pure gold 
produces no current, or rather one which quickly disappears, 
which he ascribes to accidental impurities. I have not been 
able any more than Marianini to find this circumstance con- 
firmed ; although I employed gold of 24 carats, and a nitric 
acid which when properly diluted was not rendered turbid by 
nitrate of silver. Fresh surfaces were given to the metals by 
rubbing them with dry sand-paper (I expressly avoided treat- 
ing them with acids to clean them, because in this case pecu- 
liar variations of surfaces are to be feared). The divergence 
which at the beginning was very lively, decreased, it is true, 
considerably, very soon, but remained still constantly in 
favour of the positive relation of the gold. A very sen- 
sitive multiplier of several thousand coils, however, was em- 
ployed. With the same instrument I have observed an ac- 
tion not inconsiderable between gold and platina in rectified 
muriatic acid, which however with a multiplier of a medium 
number of coils but of thicker wire, was scarcely percep- 
tible. The reasons from Ohm's theory may be sufficiently 
well known with us to lead us to expect, that, in fact, in this 
case, where the circuit includes in itself a considerable op- 
position, we can expect action only from a multiplier with 
immerous coils, even when of thin wire. 

Notwithstanding, however, that De la Rive, under the cir- 
cumstances of his experiment, could observe no action of a 
gold and platinum circuit, he would undoubtedly have ob- 
served it, if he had saturated this acid with nitrate of silver 
in excess, in which case, in fact, in all appearance opposed 
to the chemical theory, a not less considerable divergence is 
obtained than if gold and platinum are connected in a solu- 
tion of nitrate of silver only. I am, however, far from giving 
these circumstances an importance against the chemical theory, 
equivalent to that which experiments of apparently an op- 
posed kind are made to have in favour of it, for it is certain 
that a solution of nitrate of silver exerts a modified influence 
on the surfaces of gold and platinum, although this is op- 



S74 G. Th. Fechner's Justification of the 

posed to the common notions of chemistry. It now remains 
only to determine whether this changing action of the fluid on 
the metal is also the cause of the current. That a solution of 
nitrate of silver really effects a change of electrical state in gold 
and platinum, will be seen from the following circumstances : 

Gold is negative to platinum in a concentrated solution of 
nitrate of silver ( ) part salt to 8 water) as also in a solution 
in some degree diluted, and finally also in nitric acid saturated 
to excess with a solution of nitrate of silver; on employing a 
solution of nitrate of silver greatly diluted a reversion occurs 

from platinum gold into platinum gold. There are many 
other proofs of the resulting change of the platinum to 
positive, which I shall here however neglect. Moreover, my 
experiments have taught me that even the noble metals are 
capable of undergoing the most remarkable electro-chemical 
changes in fluids which have generally been considered as 
devoid of action upon them. It would however lead us too 
far were we to treat on this subject at present. 

It is evident from all of the above, that with the present 
state of science experiments on the weaker or smaller galvanic 
activity of circuits in fluids of apparently greater or smaller 
chemical activity cannot give certain results either favourable 
or unfavourable to the chemical theory. The principal ob- 
ject is to discover the cause of the peculiar changes which in 
many cases the general condition of the metals would not 
lead us to expect, that metals undergo in fluids, before we 
can make use of the condition so acquired for the explanation 
of other circumstances. 

4. The following experiment against the chemical theory 
I made known a long time ago in Schweigger's Journal, vol. 
Ivii. p. 9, and I should not publish it anew if it had been 
noticed by any one of the supporters of that theory, which 
makes me suppose that it is but little known. This experi- 
ment, so easily repeated, and which I annually perform as a 
class experiment, appears to me to be exactly an experimenttim 
cnicis against the chemical theory.* 

Let an equal number of pairs of zinc and copper plates 
(I generally employ ten) be arranged in a couronne des tasses 
so as to form a compound circuit arranged as a pile ; so, how- 
ever, that the one half of the elements tends to produce a cur- 
rent opposed to that of the other. Let the conducting fluid 
be water. If evei'ything is the same in all the cells, the two 
opposite currents will compensate each other in action at the 
connecting multiplier and will produce no divergence. It 

* See Prof. Schoenbein's remarks on this experiment, in p. 162. 



Contact Theory of Galvanism. 375 

happens at times that current equilibrium is obtained very ex- 
actly, and then this equilibrium continues even when any 
quantity of muriatic acid is added to the fluid contained in 
one of the systems; the one system may even be filled much 
higher with dilute acid than that producing the opposite cur- 
rent is with water. It is true that an ascendency of the one 
current is gradually developed, undoubtedly in consequence of 
the changing action of the muriatic acid upon the plates, hut 
it is not the cells with acid, in which a tumultuous development 
of gas takes place, but the water-cells which obtain this ascend- 
ency. If on the other hand each half of the cells is con- 
nected by itself by the multiplier, that instrument experiences 
from the acid cells a very stormy action, from the water-cells 
a weak action merely. How then the result of this experi- 
ment is to be explained accoi'ding to the chemical theory, 
I cannot conceive. According to the theory of contact the 
explanation is easy. For according to this the addition of 
muriatic acid increases the action only by diminishing the 
opposition to the conduction present in the circuit, and this 
diminution is of as great advantage to the electricity (which is 
developed by contact in the ceils without acid,) in its entire 
circulation through the circuit, as the electricity of the pairs 
of plates which are in the very acid fluid. We do not always 
succeed in meeting with such homogeneous plates, that when 
in the beginning everything has been equalized, equilibrium 
shall exist between the pairs of plates of the one and the 
other side. Frequently, previous to the addition of the acid 
in the cells of the one system, a certain side, in which the 
pairs have a somewhat more powerful electro-motive state, 
has an ascendency, although if proper precautions have been 
taken this is very weak. In this case, however, the experi- 
ment can be rendered available for our purpose quite as well 
by adding at present the acid to that series of cells which ap- 
pears to be the weakest. According to the chemical theory, 
the divergence of the multiplier should now quickly be re- 
versed, instead of which it increases in the very direction which 
it previously had. 

I will add yet the following variation of this experiment, 
connected with a measurement. 

On one side five pairs of zinc and copper plates werearranged 
in a couronne des tasses, on the other five pairs of zinc and tin 
plates. The vessels of the first system were now filled only 
a third part as high as those of the second, the first with 
common spring water, the latter with strongly acidulated 
water, which caused a very lively development of gas. The 
first five plates connected by themselves into a circuit gave 



376 G. Th. Fechner's Justification of the 

a curi'ent which, measured by a multipher by means of the 
initial oscillations, equalled 1*41 (reckoning the action of the 
earth upon the needles of the multiplier =1); the second 
system, forming a circuit by itself, produced a current, the 
force of which measured in the same manner was expressed 
by 44'7. When both circuits were combined into one with 
opposed direction of the current, it was evident that the pairs 
of zinc and copper plates still retained the ascendency. The 
measure of the current resulting from the difference was 
0-45. 

5. Although the increase of chemical action in common 
circuits, not connected by too bad a conductor, indicates a 
very remarkable influence on the increase of their power, yet 
this favourable influence is lost in proportion to the increased 
opposition in the connecting conductor; thus, for instance, 
the power of the current of a circuit rose, by connexion with 
proportionally short and thick wire, by the addition of a cer- 
tain quantity of acid, in the proportion of 1 : 191. (The 
plates were newly filed before the introduction of the acid, 
and the power, as in the first case, measured by the initial oscil- 
lations only.) As the same experiment was repeated, under 
quite the same circumstances, but by connecting the poles 
with a very long and thin wire which evinced about 7000 
times the opposition of the former, the power rose by equal 
strength of the fluid only in the proportion of 1:1^ (other 
examples of this kind are enumerated in my galvanic mea- 
surements). In the whole chemical theory 1 find no reason 
why the ■proportion of the increase of power should not be 
the same in both cases. With respect to the contact theory, 
according to which by increasing the strength of the fluid 
there is no increase in the quantity of electricity developed, 
but only a diminution of part of the opposition to the conduc- 
tion existing in the circuit, no difficulty here presents itself, 
since the diminution of a part of the entire conductive opposition 
must lose influence in increasing the power of the circuit, in 
the ratio of its smaller amount in proportion to the other parts 
of the opposition of the circuit. Jf we lengthen the con- 
necting wire more and more, it may at last be diminished so 
greatly that the opposition of the fluid becomes insensible. 

III. On the Development of Electricity hy the Contact of Metals 
isoith Fluids. 

There still remains for me to notice some experiments 
which have been enumerated as beai'ing against the theory 
of contact, but which, properly speaking, merely prove (per- 
haps even appear nierely to prove) : 



Contact Theory of Galvanisiyi. 377 

1. That it is not solely the contact of metals, or, generally, 
solid bodies with one another, which is capable of developing 
electricity. 

2. That the excitation of electricity caused by the fluids, 
whether from their mutual contact, or from contact with solid 
bodies, does not follow exactly the same laws as that which 
arises from the mutual contact of solid bodies. The first is 
merely a generalization of the theory of contact, already made 
by Yolta; the latter is no objection against it, since we do 
not know what influence the aggregate state has upon the still 
obscure process of the development of electricity. Expe- 
rience certainly shows, undoubtedly, that fluids are not ame- 
nable to the same law of galvanic tension as solid bodies, or that 
if such is the case, secondary consequences resulting from the 
mobility of the particles, changes of metallic surface, or other 
circumstances, modify the result. The latter is my opinion, 
of which I have given a general explanation (although with- 
out paying sufiicient attention to the changes of metals) in Blot's 
Lehrbuch {Precis), Part III. p. 321. 372., and which, up to the 
present time, I have found no inclination to abandon. Then, 
almost all the facts recently published by Faraday appear to 
me to be for this reason much more important than they are 
represented to be by his own statements. Be this, however, 
as it may, (for I will force this view on no one) experiments in 
which we see electricity originate even without the contact of 
solid bodies, or so that this is of no influence, and, at the same 
time, thus observe the fluids acting a part different from 
that of solid bodies, cannot give proofs against the theory of 
contact. We must also consider, in this point of view, the 
following experiment by De la Rive, which 1 will relate, to- 
gether with my own observations x'especting it. It is found, 
with some little variation, in the Recherches, p. 62. 

" To each end of a wooden cylinder, of from 10 to J 2 cen- 
timetres in length, and 1 to 2 centimetres in diameter, I fast- 
ened a plate of zinc, which terminated outwards in a soldered 
brass point; taking at present the brass point of the one plate 
in my hand, 1 touched the condenser (also of brass) with the 
brass point of the other. According to the theory of contact, 
I ought to have obtained no sign of electrical activity, both 
the zinc and the brass plates lying opposite to each other, 
and being united by an insulated piece of wood which perform- 
ed the office of conductor between both plates. Because, how- 
ever, the one end of the wooden cylinder was moister than the 
other, I obtained signs of electricity, the nature of which bore 
a constant ratio to the chemical action, which was excited by 
the contact of the carefully brightened zinc with the moist 



378 G. Th. Fechner on the Contact Theory of Galvanism. 

wood. These signs of electricity were negative, when I held 
between the fingers the brass point of that zinc plate, the other 
end of which was fastened in the less moist part of the wood. 
For the success of this experiment, it is necessary that the 
wood be somewhat moist ; the moisture which it attracts from 
the air is perfectly sufficient; care must also be taken that the 
one end of the wood be kept drier than the other." 

The truth of the result of the following, certainly interest- 
ing experiment, has been doubted, but it is certainly correct, 
as I have often convinced myself by a frequent and more care- 
ful repetition of it in the following easy manner. 

Upon the zinc surface of a soldered zinc and copper plate 
were laid three or four equally large or somewhat larger leaves 
of air-dried writing paper, the top one moistened with distilled 
water, and upon this was placed, by the zinc surface, a 
second soldered zinc and copper plate ; so that a system of 
the following order was formed : copper, zinc, dry paper, 
moist paper, zinc, copper. The zinc and copper were filed 
quite bright, and I had convinced myself that if I tried the 
system omitting the moist paper, at the copper condenser no 
development of electricity could be detected. When, however, 
I now applied the system with the inserted moist paper to the 
condenser in such a manner that the double plate lying on the 
moist paper came into connexion with it, while the other 
double plate stood in connexion with the earth by means of 
the fingers, either air-dried or sprinkled with distilled water, 
there was obtained, in accordance with De la Rive, a negative 
divergence, and a positive one on the contrary by reversion of 
the system. The same phaenomena took place, if instead of 
distilled water I employed water acidulated by nitric acid for 
the purpose of moistening. 

These experiments I have also varied and simplified in the 
following way: 

Between two zinc plates, without copper, were arranged 
several layers of air-dried writing paper, and the one extreme 
layer on which lay the zinc plate was moistened with distilled 
or nitric-acid ulate water. Sometimes the zinc plate situated 
on the dry, sometimes that situatedon the moist layer of paper 
was put in connexion with a condenser of zinc. This expe- 
riment, still more simplified, may be performed as follows : 
let a zinc rod be wound round at one end with air-dried 
blotting paper; at the other, with blotting paper which has 
been moistened with spring or with distilled water. Accord- 
ing now to the circumstance whether the dry or wet paper is 
discharged at the (brass) condenser, while at the same time 
the other paper is held with the fingers, do we obtain a posi- 



Dr. G. Bird on certain Properties of Platina Electrodes. 379 

tive or negative divergence. The discharge took place in both 
my cases on a leaf of writing paper moistened with distilled 
water, which was applied to the inferior plate of the condenser, 
while another leaf of moist paper covering the upper plate was 
touched with the fingers in order to make everything alike on 
both sides with respect to the condenser. The most simple 
form of the experiment might however be this ; that a zinc 
condenser plate should be immediately touched with the moist 
fingers, which, as others have already observed, is sufficient to 
produce a negative shock. I do not say that this experiment 
is as yet explained agreeably to the contact theory, but as little 
could any one find in it a proof of the chemical theory. More- 
over, this may be viewed in connexion with other much more 
important experiments which promise at least a partial ex- 
planation of it, of which, however, it is not now my intention 
to treat. 



L. Observations on some peculiar Properties acquired hy 
Plates of Platina^ 'which have been used as the Electrodes 
of a Voltaic Battery. By Golding Bird, M.D.F.L.S. F. G.S.y 
Sfc, Lecturer on Natural Philosophy at Guy's Hospital. 

THHE influence of platina positive electrodes in effect- 
^ ing the combination of oxygen and hydrogen are well 
known to philosophers ; some phsenomena which may be pro- 
bably referred to the same class have lately fallen under my 
notice, and are interesting from their appearing to prove that 
metals which have served as electrodes retain a polar state 
long after connexion with the battery is broken. 

It was stated some time ago in a philosophical journal that 
when the platina plates of the ordinary apparatus used for ex- 
hibiting the decomposition of water by voltaic electricity on 
the lecture table, were placed in conducting communication 
with a piece of zinc immersed in the acidulated water with 
which the apparatus was filled, the hydi'ogen evolved at the 
surface of one plate was twice the volume of that given off" at 
the other. The author of this statement added that he was 
unable to give any explanation of the fact, nor did he offer 
any remarks upon it. This phaenomenon appeared to be of 
sufficient interest to deserve a more extended examination, 
and 1 have had the pleasure of observing several curious facts 
in connexion with it. 

Exp. 1. A glass basin was furnished with two equal sized 
plates of platina passing through its bottom 1 '5 inches apart, 
each connected by copper wires to a brass cup for holding 



380 Dr. G. Bird oji certain Properties acquired by the 

mercury ; these cups, and the platina plates connected with 
them, may be called respectively A and B. 'The basin was 
filled with dilute sulphuric acid, and a tube full of the same 
fluid inverted over each plate of platina ; a rod of amalgamated 
zinc, lo one end of which was soldered two thin copper wires, 
was immersed in the contents of the basin, and the ends of 
the wires dipped into the cups of mercury A and B, by which 
the rod became metallically connected with the platina plates. 
Rapid decomposition of water instantly commenced, bubbles 
of hydrogen being evolved from the platina surfaces: in five 
minutes the tubes were examined, and instead of the gas col- 
lected being in equal volume in either tube, as would a priori 
be expected, I found, as stated by the original observer, that 
one contained nearly twice as much as the other. 

Upon reflecting on this experiment, I suspected that as the 
apparatus had been employed as a volta-electrometer a short 
time previoush^, the platina plates might have assumed and 
retained some peculiar state from their connexion with the 
battery. 

Exp. 2. The basin filled with the dilute acid was connected 
with a battery of six alternations of zinc and copper, separated 
by jars of porous earthenware and excited by sulphate of 
copper and sulphate of soda; the cup A was connected with 
the negative, and B with the positive wire : decomposition of 
water was allowed to proceed for a few minutes, contact was 
then broken with the battery : the tubes filled with diluted 
acid were inverted over the respective plates and the amal- 
gamated zinc immersed in the acid, its wires dipping into A 
and B. Hydrogen was copiously evolved at the surfaces of 
the platina, and in 10 minutes the zinc was removed. 

In the tube over the plate A was collected 1 • inch hydrogen. 

B 2-15 ^— 

During the evolution of gas, the difference in the appear- 
ance of the bubbles from the two plates was remarkable : those 
from the plate B were large, rose rapidly to the top of the 
tube, and were given off" from isolated points of the electrode ; 
whilst those from A were small, rose much slower in the 
tube, and were given off" from every part of the plate, re- 
sembling the bubbles of oxygen evolved in the voltaic decom- 
position of water. It is remarkable that the platina plate (A), 
which when in connexion with the battery gave off" the great- 
est volume of gas, (hydrogen) now evolved the smallest, and 
that (B), which had evolved the smallest (oxygen), now gave 
off" twice the volume of the other. It is needless to state that 
the gas in both tubes was hydrogen. 

Exp. S. The apparatus was refilled, again connected with 



Platina Electrodes of a Voltaic Battery. 381 

the battery, the plate A to the positive and B to the negative 
for a few minutes ; the connexions being broken, the zinc rod 
was immersed as in the last experiment, its wires dipping into 
the cups A and B ; iiydrogen was again evolved and collected 
in the tubes. 

In that over the plate A was found 2*1 

B 1-0 

These experiments clearly pointed out, that the cause of 
the difference in volume of evolved hydrogen was to be sought 
in some change produced by connexion with the battery; 
what that change consisted in was less obvious. I suspected 
that a polar state might probably have been communicated to 
the electrodes by the passage of the battery current. 

Exp. 4. The cups A and B were again connected with the 
battery, A with the negative, B with tlie positive wire for a 
few minutes ; the connexions were then broken, and a galvano- 
meter of very delicate construction connected with the cups. 
The needles instantly deviated with considerable velocity to 
90° ; the connexion was broken, and in 1 minute renewed with 
the galvanometer ; the needles deviated to the same amount 
but with less velocity. In 3 minutes, con